VLAN & VTP Questions
Here you will find answers to VLAN & VTP Questions
Question 1
Which of these best describes the actions taken when a VTP message is received on a switch configured with the VTP mode “transparent”?
A. VTP updates are ignored and forwarded out all ports.
B. VTP updates are ignored and forwarded out trunks only.
C. VTP updates are made to the VLAN database and are forwarded out trunks only.
D. VTP updates are ignored and are not forwarded.
Answer: B
Question 2
Refer to the exhibit. Catalyst R is the root bridge for both VLAN 1 and VLAN 2. What is the easiest way to load-share traffic across both trunks and maintain redundancy in case a link fails, without using any type of EtherChannel link-bundling?
A. Increase the root bridge priority (increasing the numerical priority number) for VLAN 2 on Catalyst D so that port D2 becomes the root port on Catalyst D for VLAN 2.
B. Decrease the port priority on R2 for VLAN 2 on Catalyst R so that port D1 will be blocked for VLAN 2 and port D2 will remain blocked for VLAN 1.
C. Decrease the path cost on R2 on Catalyst R for VLAN 2 so that port D1 will be blocked for VLAN 2 and port D2 will remain blocked for VLAN 1.
D. Increase the root bridge priority (decreasing the numerical priority number) for VLAN 2 on Catalyst R so that R2 becomes the root port on Catalyst D for VLAN 2.
Answer: B
Explanation
First we should understand what will happen if nothing is configured (use default values). Because R is the root bridge so all of its ports will forward. D will need to block one of its ports to avoid a bridging loop between the two switches. But how does D select its blocked port? Well, the answer is based on the BPDUs it receives from R. A BPDU is superior than another if it has:
1. A lower Root Bridge ID
2. A lower path cost to the Root
3. A lower Sending Bridge ID
4. A lower Sending Port ID
These four parameters are examined in order. In this case, all the BPDUs sent by R have the same Root Bridge ID, same path cost to the Root and same Sending Bridge ID. The only parameter left to select the best one is the Sending Port ID (Port ID = port priority + port index). If using default values, the default port priority’s value is 32 or 128 (128 is much more popular today), so D will compare port index values, which are unique to each port on the switch, and because port R2 is inferior to port R1 (the port’s number of R2 is higher than that of R1, for example port Fa0/2 is inferior to port Fa0/1), D will select the port connected with port R1 as its root port and block the other port.
The problem here is port D2 is blocked for both VLAN 1 & 2 and that means we can’t use the underneath link for load-sharing. The underneath link is just used in the case the above link fails.
Now as you can guess, the easiest way to load-share traffic across both trunks is decreasing the port priority on R2 for VLAN 2 on Catalyst R so that port D1 will be blocked for VLAN 2. Notice that “decreasing” here means make that port ID superior to the other port.
Question 3
The network administrator is trying to add Switch1 to the network, but the 802.1 Q trunk is not coming up. Switch1 was previously tested in the laboratory and its trunk configuration worked fine. What are three possible causes of this problem? (Choose three)
A. The trunking configuration mode on Switch1 is set to Off.
B. The trunking configuration mode on the other end is set to On.
C. The trunking configuration mode on the other end is set to Desirable.
D. Cisco Discovery Protocol is not running on the other end.
E. There is a VTP domain name mismatch.
F. Switch1 does not support 802.1Q.
Answer: B C E
Explanation
There are 5 possible trunking modes for a switch port:
+ Auto: this is the default mode. In this mode, a port will become a trunk port if the device the port is connected to is set to the on or desirable mode.
+ Desirable: allows the port to become a trunk port if the device the port is connected to is set to the on, desirable, or auto mode
+ On: sets the port to permanent trunking mode.
+ Nonegotiate: sets the port to permanent trunking mode without sending Dynamic Trunking Protocol (DTP) frames
+ Off: sets the port to permanent non-trunking mode
In this case, we can guess the trunking mode of Switch 1 is “auto” (default mode). When in the laboratory, the trunking mode of the other end is set to “On” or “Desirable” so 2 switches can negotiate and the link becomes trunk with no problem. But when plugging to the network, other switches may have the trunking mode set to “auto” so the 802.1Q trunk is not coming up -> B C are correct.
Of course these switches need to be in the same VTP domain so that they can “talk” with each other -> E is correct.
Question 4
Refer to the exhibit. The Layer 2 network uses VTP to manage its VLAN database. A network designer created all VLANs on the VTP server (switch 1) and it has been advertised through VTP to all other VTP clients (switches 2 through 4). Due to network growth, a network operator decided to add a new switch between switch 1 and switch 3. The network operator has been instructed to use a refurbished switch and use a VTP client. Which three of these factors should the network operator consider to minimize the impact of adding a new switch? (Choose three)
A. Pay special attention to the VTP revision number, because the higher value takes the priority.
B. Configure all VLANs manually on the new switch in order to avoid connectivity issues.
C. A trunk should be established between the new switch and switches 1 and 3 as VTP only runs over trunk links.
D. Set at least the VTP domain name and password to get the new switch synchronized.
E. An ISL trunk should be established between the new switch and switches 1 and 3, because VTP only runs over ISL.
F. Pay special attention to the VTP revision number, because the lower value takes the priority.
Answer: A C D
Explanation
VTP should be used whenever we have more than 1 switch with multiple VLANs. It helps us save much time so configuring all VLANs manually is just a waste of time -> B is not correct.
VLAN Trunking Protocol (VTP) can operate over 802.1q or ISL on FastEthernet link.
+ On ISL: Switch(config-if)#switchport trunk encapsulation isl
+ On 802.1q: Switch(config-if)#switchport trunk encapsulation dot1q
-> E is not correct
Note: The 2940/2950 switches only support 802.1q encapsulation with the switchport mode trunk command. The switch will automatically use 802.1q encapsulation.
Each time a VTP updates are sent out, the revision number is increased by 1. Any time a switch sees a higher revision
number, it knows the information that it’s receiving is more current, and it will overwrite the current database with that new information.
can you please give explanation for Question 2
thanks
Can anyone explain Q.3? I hope someone will,,
I believe the answers to Q3 are wrong.
Ports configured for trunking ON or DESIRABLE will form a trunk with any port configured for any mode but OFF.
Hello!
The answers to Q3 are correct.
If you have on one side “ON” and on the other side “DESIRABLE” a trunk will not form.
“Desirable” actively tries to form a trunk, but the “ON” side does not reply because it is configured to put the interfaces in TRUNK without questioning why.
Only desirable-desirable and desirable-auto will form a trunk.
Also auto-auto will not form a trunk.
Hope it helps!
Disagree … ON-DESIRABLE will form a trunk
“switchport mode trunk” will send DTP unless u add switchport nonnegotiate.
Q3 is wrong.
I agree with chris
I agree with Chris too concerning question 3.
If the other ends are set to “on” or “desirable” the trunk will form. The explanation above totally contradicts itself by stating how the modes work and then choosing the answers that are opposite of the explanation. My guess would then have to be A, E, and F just from process of elimination.
First things first… Switch1 was working in the lab. Unfortunately the assumption that Switch1 was set to auto, I think is wrong.
A. The trunking configuration mode on Switch1 is set to Off. ( THIS CAN NOT BE Correct! Why? Switch1 had a dot1q trunk up in the lab!)
B. The trunking configuration mode on the other end is set to On. ( This would be correct if Switch1 is set to NO NEG!) – On requires a DTP “response” from the other end… NO NEG will NOT send a “response” ; )
C. The trunking configuration mode on the other end is set to Desirable. ( This would be correct if Switch1 is set to NO NEG!) Desirable requires a DTP “response” from the other end… NO NEG will NOT send a “response” ; )
D. Cisco Discovery Protocol is not running on the other end. – Trunks do not require CDP! Go ask a CCNA about this one if your not sure.
E. There is a VTP domain name mismatch. – Trunks will not form if there are “competing” VTP domains
F. Switch1 does not support 802.1Q. ( THIS CAN NOT BE Correct! Why? Switch1 had a dot1q trunk up in the lab!)
B C E ARE CORRECT ! ! !
Having read the question no 3 I myself jumped in to a confussion as one of the things is we dont know how switch was configured and if I were the administrator I would check the switch configuration and check with the other end.
for Q.2
I think C is correct as well
We can use the command
#spanning−tree vlan 2 cost
plz advise.
On q2
changing the cost will not have any effect
Since R is the root bridge the cost to the root bridge is 0. It adds the port cost on received BPDU not on sent ones. So switch R will send with 0, switch D will add his cost when it gets the BPDU, if switch D were to send it out to another switch it would send this value.. ie 0+cost and the next switch say W would then add its cost as it received it. ie 0+cost-d+cost-w
You would have to make the change on switch D which is not a option in this case.
I got your point, Thank you Bill.
about Q.2
according to cisco answer C is also valid. Any suggestions….
http://www.cisco.com/en/US/docs/switches/lan/catalyst2950/software/release/12.1_9_ea1/configuration/guide/swvlan.html#wpxref66494
All I can say about q.2 is to try it on some real switches. The link cost is added to the cost received in BPDU. It is INBOUND option. The root bridge will always transmit a value of zero no matter what you set the cost.
Regarding Q2.
Some info (http://www.ciscopress.com/articles/article.asp?p=29803&seqNum=3)
ON —- ON/Desirable/Auto =>Trunk
Desirable — ON/Desirable/Auto => Trunk
Auto — ON/Desirable => Trunk
No Neg — ON/NoNeg =>Trunk
Now again looking at the options, the best way is to “Eliminate” wrong ones.So options A,D,F are obviously wrong.
But the catch, if other end is ON (option B), there is no way that Trunk “won’t” be formed, which takes us back to option A that the trunk mode was turned “OFF” in Switch 1 somehow.(Mind that the other 2 options still remains wrong).
TRICKY 😀
^^ Question 3.
Just notice that, there is hardly any difference between ON and Desirable.But the difference is that, the mode “ON” will make the port Trunk – Unconditionally and will tag the outgoing frames.While the mode Desirable will be actively looking for Trunk and if not found, it will move to non Trunking mode after 5 minutes.
The only way to answer Q3 is to assume the other switch uses ‘ON-Nonegotiate’. This makes B, C and E the only possible answers because:
1 – If, as in A, OFF was the trunking mode set on the switch then no trunking could possibly be formed in the Test lab.
2 – As CDP has nothing to do with DTP or Trunking in any way, D can’t be correct.
3 – Dot1Q has to be supported as, again, in the Test lab it worked.
This leaves only B, C and E.
The question is another example of Cisco’s poor questions. The ‘ON’ and ‘ON-Nonegotiate’ variations of ‘ON’ are not explicitly stated so you have to ‘twist’ the question’s structure to solve this…and in a real exam do you really have 5 mins and some to work this out, logically exclude answers, go back and re-work the question based on this???
No Neg — ON/NoNeg =>Trunk
Just have a look at this, so even if SW1 is in “ON-Nonegotiate” it will form trunk if the other end is just “ON” (even with Nonegotiate – check the link)
So, B cannot be.
without*
Regarding the lab scenario, I guess the questioner just wanted to let us know that the switch support trunking, but that doesn’t give the guarantee that the trunk mode wasn’t kept “OFF” during real time, a possible guess.
🙂 Anyways i am done with this question.
Q3. When remembering this chart. I always think of Auto has a “Passive Mode”, where he will listen to DTP messages but will not initiate them. This is whey Auto-Auto doesn’t work. When one side is in auto, it needs the other side to run DTP or initiate DTP. So auto-on or auto-desirable works.
But there is an easier way to look at it. Eliminate the “Bad” answers first.
Answers D is clearly wrong, CDP is not needed. The switch config was working in the lab, it would not work in the lab with answer A. So A is also wrong, and it would not work in the lab if it didn’t support 802.1q. That really leaves only B, C and E has your possible three answers.
A. The trunking configuration mode on Switch1 is set to Off.
B. The trunking configuration mode on the other end is set to On.
C. The trunking configuration mode on the other end is set to Desirable.
D. Cisco Discovery Protocol is not running on the other end.
E. There is a VTP domain name mismatch.
F. Switch1 does not support 802.1Q.
On – place the port to trunk and try to negiotiate even other port not trunk it will place this port trunk. DTP generated – Trunking, unconditionally.
Calling all cars, clanlig all cars, we’re ready to make a deal.
Now we know who the sensilbe one is here. Great post!
First, I don’t have any switches that supports DTP (dynamic trunking protocol) to verify the finding/solution in the lab, but I would appreciate if someone could validate them:
Now lets go over the five information I acquired from paper research that couldn’t be validated:
1. Negotiation can NOT be turned off when using Auto or Desirable Trunk mode.
2. The interface switchport mode configured to Auto on both end will resolve to Access on both side.
3. The interface switchport mode configured to Desirable on both end will resolve to Trunk on both side.
4. The interface switchport mode configured to Auto on one end and Desirable on the other end will resolve to Trunk on both side.
5. The interface switchport mode configured to Auto or Desirable will resolve to Access if no negotiation happens. This could be possible if the other end of the switch has negotiation turned off.
Now let’s go over the choices:
A. Technically this choice might be true. This wouldn’t be the first time Cisco question contradicted it’s choices. – LOL
B. This choice might be true if my research is correct. Switch1 is set to auto/desirable and the other end is set to ON with negotiation turned off will cause mismatch (Access-Trunk).
C. This choice might be true if my research is correct. Switch1 is set to ON with negotiation turned off and the other end is set to desirable will cause mismatch (Trunk-Access).
D. This choice is clearly false, since CDP has nothing to do with interface switchport mode.
E. Although I have seen otherwise, it appears majority, including Cisco documentation, is saying this choice is the right answer.
F. Technically this choice might be true. The question did not state the laboratory test was using 802.1Q.
Personally, I will go with B, C, E, but the right answer is what ever Cisco say they are, even if they are wrong. Have I mentioned, I hate this question.
Here’s testing on actual, live 3560’s, sitting on my desk, in support of question number 3. This is a little long, and I tried to add in some comments highlighting different scenarios. Hope this helps.
—————
==================================================
= Section – 2 3560’s Fresh out of Box (Foob)
==================================================
Switch_1#
Switch_1#
Switch_1#
Switch_1#sh inv
NAME: “1”, DESCR: “WS-C3560X-48P”
PID: WS-C3560X-48P-L , VID: V02 , SN: xxxxxxxxxxxxxxx
NAME: “Power Supply 0”, DESCR: “FRU Power Supply”
PID: C3KX-PWR-715WAC , VID: V01 , SN: xxxxxxxxxxxxxxxx
NAME: “FRULink Slot 1 – FRULink Module”, DESCR: “FRULink 1G Module”
PID: C3KX-NM-1G , VID: V01 , SN: xxxxxxxxxxxxxxxxxxxxxx
Switch_1#sh ver
Cisco IOS Software, C3560E Software (C3560E-UNIVERSALK9-M), Version 12.2(55)SE3, RELEASE SOFTWARE (fc1)
….
ROM: Bootstrap program is C3560E boot loader
BOOTLDR: C3560E Boot Loader (C3560X-HBOOT-M) Version 12.2(53r)SE2, RELEASE SOFTWARE (fc1)
…
System image file is “flash:/c3560e-universalk9-mz.122-55.SE3/c3560e-universalk9-mz.122-55.SE3.bin”
===============================================================
Switch_1#sh run int gi 0/1
Building configuration…
Current configuration : 36 bytes
!
interface GigabitEthernet0/1
end
Switch_1#
% Ambiguous command: “sh int gi 0/1 tr”
Switch_1#sh int gi 0/1 trun
Port Mode Encapsulation Status Native vlan
Gi0/1 auto negotiate other 1
Port Vlans allowed on trunk
Gi0/1 none
Port Vlans allowed and active in management domain
Gi0/1 none
Port Vlans in spanning tree forwarding state and not pruned
Gi0/1 none
Switch_1#
Switch_1#
Switch_1#
Switch_1#
Switch_1#sh int gi 0/1 swit
Switch_1#sh int gi 0/1 switchport
Name: Gi0/1
Switchport: Enabled
Administrative Mode: dynamic auto
Operational Mode: down
Administrative Trunking Encapsulation: negotiate
Negotiation of Trunking: On
Access Mode VLAN: 1 (default)
Trunking Native Mode VLAN: 1 (default)
Administrative Native VLAN tagging: enabled
Voice VLAN: none
Administrative private-vlan host-association: none
Administrative private-vlan mapping: none
Administrative private-vlan trunk native VLAN: none
Administrative private-vlan trunk Native VLAN tagging: enabled
Administrative private-vlan trunk encapsulation: dot1q
Administrative private-vlan trunk normal VLANs: none
Administrative private-vlan trunk associations: none
Administrative private-vlan trunk mappings: none
Operational private-vlan: none
Trunking VLANs Enabled: ALL
Pruning VLANs Enabled: 2-1001
Capture Mode Disabled
Capture VLANs Allowed: ALL
Protected: false
Unknown unicast blocked: disabled
Unknown multicast blocked: disabled
Appliance trust: none
Switch_1#
Switch_2#sh run int gi 0/1
Building configuration…
Current configuration : 36 bytes
!
interface GigabitEthernet0/1
end
Switch_2#sh int gi 0/1 trunk
Port Mode Encapsulation Status Native vlan
Gi0/1 auto negotiate other 1
Switch_2#sh int gi 0/1 switchport
Name: Gi0/1
Switchport: Enabled
Administrative Mode: dynamic auto
Operational Mode: down
Administrative Trunking Encapsulation: negotiate
Negotiation of Trunking: On
Access Mode VLAN: 1 (default)
Trunking Native Mode VLAN: 1 (default)
Administrative Native VLAN tagging: enabled
Voice VLAN: none
Administrative private-vlan host-association: none
Administrative private-vlan mapping: none
Administrative private-vlan trunk native VLAN: none
Administrative private-vlan trunk Native VLAN tagging: enabled
Administrative private-vlan trunk encapsulation: dot1q
Administrative private-vlan trunk normal VLANs: none
Administrative private-vlan trunk associations: none
Administrative private-vlan trunk mappings: none
Operational private-vlan: none
Trunking VLANs Enabled: ALL
Pruning VLANs Enabled: 2-1001
Capture Mode Disabled
Capture VLANs Allowed: ALL
Protected: false
Unknown unicast blocked: disabled
Unknown multicast blocked: disabled
Appliance trust: none
Switch_2#
=========================================
= Auto/Auto test – default configuration
=========================================
plugged in – default config
——————
Switch_1#sh run int gi 0/1
Building configuration…
Current configuration : 36 bytes
!
interface GigabitEthernet0/1
end
Switch_1#sh int gi 0/1 switchport
Name: Gi0/1
Switchport: Enabled
Administrative Mode: dynamic auto
Operational Mode: static access
Administrative Trunking Encapsulation: negotiate
Operational Trunking Encapsulation: native
Negotiation of Trunking: On
Access Mode VLAN: 1 (default)
Trunking Native Mode VLAN: 1 (default)
Administrative Native VLAN tagging: enabled
Voice VLAN: none
Administrative private-vlan host-association: none
Administrative private-vlan mapping: none
Administrative private-vlan trunk native VLAN: none
Administrative private-vlan trunk Native VLAN tagging: enabled
Administrative private-vlan trunk encapsulation: dot1q
Administrative private-vlan trunk normal VLANs: none
Administrative private-vlan trunk associations: none
Administrative private-vlan trunk mappings: none
Operational private-vlan: none
Trunking VLANs Enabled: ALL
Pruning VLANs Enabled: 2-1001
Capture Mode Disabled
Capture VLANs Allowed: ALL
Protected: false
Unknown unicast blocked: disabled
Unknown multicast blocked: disabled
Appliance trust: none
Switch_1#
Switch_1#
Switch_1#
Switch_1#sh int status | i 0/1_
Gi0/1 connected 1 a-full a-1000 10/100/1000BaseTX
————–
Switch_2#sh int status | i Gi0/1_
Gi0/1 connected 1 a-full a-1000 10/100/1000BaseTX
Switch_2#
Switch_2#
Switch_2#
Switch_2#sh int gi 0/1 swit
Name: Gi0/1
Switchport: Enabled
Administrative Mode: dynamic auto
Operational Mode: static access
Administrative Trunking Encapsulation: negotiate
Operational Trunking Encapsulation: native
Negotiation of Trunking: On
Access Mode VLAN: 1 (default)
Trunking Native Mode VLAN: 1 (default)
Administrative Native VLAN tagging: enabled
Voice VLAN: none
Administrative private-vlan host-association: none
Administrative private-vlan mapping: none
Administrative private-vlan trunk native VLAN: none
Administrative private-vlan trunk Native VLAN tagging: enabled
Administrative private-vlan trunk encapsulation: dot1q
Administrative private-vlan trunk normal VLANs: none
Administrative private-vlan trunk associations: none
Administrative private-vlan trunk mappings: none
Operational private-vlan: none
Trunking VLANs Enabled: ALL
Pruning VLANs Enabled: 2-1001
Capture Mode Disabled
Capture VLANs Allowed: ALL
Protected: false
Unknown unicast blocked: disabled
Unknown multicast blocked: disabled
Appliance trust: none
Switch_2#
=====================================================
= Testing Changing one side ON, other side Auto
=====================================================
Changing int gi 0/1 on switch 2 to “on”.
—————————-
Switch_2#
Switch_2#conf t
Enter configuration commands, one per line. End with CNTL/Z.
Switch_2(config)#int gi 0/1
Switch_2(config-if)#switchport trunk encap dot1q
Switch_2(config-if)#switchport mode trunk
Switch_2(config-if)#exit
Switch_2(config)#exit
Switch_2#
*Mar 1 01:04:18.029: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/1, changed state to down
Switch_2#
*Mar 1 01:04:19.120: %SYS-5-CONFIG_I: Configured from console by console
Switch_2#
*Mar 1 01:04:21.058: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/1, changed state to up
Switch_2#
Switch_2#sh int trun
Port Mode Encapsulation Status Native vlan
Gi0/1 on 802.1q trunking 1
Port Vlans allowed on trunk
Gi0/1 1-4094
Port Vlans allowed and active in management domain
Gi0/1 1
Port Vlans in spanning tree forwarding state and not pruned
Gi0/1 none
Switch_2#
Switch_2#sh int gi 0/1 swit
Name: Gi0/1
Switchport: Enabled
Administrative Mode: trunk
Operational Mode: trunk
Administrative Trunking Encapsulation: dot1q
Operational Trunking Encapsulation: dot1q
Negotiation of Trunking: On
Access Mode VLAN: 1 (default)
Trunking Native Mode VLAN: 1 (default)
Administrative Native VLAN tagging: enabled
Voice VLAN: none
Administrative private-vlan host-association: none
Administrative private-vlan mapping: none
Administrative private-vlan trunk native VLAN: none
Administrative private-vlan trunk Native VLAN tagging: enabled
Administrative private-vlan trunk encapsulation: dot1q
Administrative private-vlan trunk normal VLANs: none
Administrative private-vlan trunk associations: none
Administrative private-vlan trunk mappings: none
Operational private-vlan: none
Trunking VLANs Enabled: ALL
Pruning VLANs Enabled: 2-1001
Capture Mode Disabled
Capture VLANs Allowed: ALL
Protected: false
Unknown unicast blocked: disabled
Unknown multicast blocked: disabled
Appliance trust: none
Switch_2#
—————
Switch_1#
Switch_1#sh int trunk
Port Mode Encapsulation Status Native vlan
Gi0/1 auto n-802.1q trunking 1
Switch_1#
Switch_1#sh int gi 0/1 swit
Name: Gi0/1
Switchport: Enabled
Administrative Mode: dynamic auto
Operational Mode: trunk
Administrative Trunking Encapsulation: negotiate
Operational Trunking Encapsulation: dot1q
Negotiation of Trunking: On
Access Mode VLAN: 1 (default)
Trunking Native Mode VLAN: 1 (default)
Administrative Native VLAN tagging: enabled
Voice VLAN: none
Administrative private-vlan host-association: none
Administrative private-vlan mapping: none
Administrative private-vlan trunk native VLAN: none
Administrative private-vlan trunk Native VLAN tagging: enabled
Administrative private-vlan trunk encapsulation: dot1q
Administrative private-vlan trunk normal VLANs: none
Administrative private-vlan trunk associations: none
Administrative private-vlan trunk mappings: none
Operational private-vlan: none
Trunking VLANs Enabled: ALL
Pruning VLANs Enabled: 2-1001
Capture Mode Disabled
Capture VLANs Allowed: ALL
Protected: false
Unknown unicast blocked: disabled
Unknown multicast blocked: disabled
Appliance trust: none
Switch_1#
————————
changing switch 2 back to auto, removing config
Switch_2#
Switch_2#
Switch_2#conf t
Enter configuration commands, one per line. End with CNTL/Z.
Switch_2(config)#default int gi 0/1
Interface GigabitEthernet0/1 set to default configuration
Switch_2(config)#exit
Switch_2#
*Mar 1 01:08:01.074: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/1, changed state to down
*Mar 1 01:08:02.047: %SYS-5-CONFIG_I: Configured from console by console
Switch_2#
Switch_2#
*Mar 1 01:08:04.102: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/1, changed state to up
——————————-
Switch_2#
Switch_2#sh int trun
Switch_2#
Switch_2#sh int gi 0/1 swit
Name: Gi0/1
Switchport: Enabled
Administrative Mode: dynamic auto
Operational Mode: static access
Administrative Trunking Encapsulation: negotiate
Operational Trunking Encapsulation: native
Negotiation of Trunking: On
Access Mode VLAN: 1 (default)
Trunking Native Mode VLAN: 1 (default)
Administrative Native VLAN tagging: enabled
Voice VLAN: none
Administrative private-vlan host-association: none
Administrative private-vlan mapping: none
Administrative private-vlan trunk native VLAN: none
Administrative private-vlan trunk Native VLAN tagging: enabled
Administrative private-vlan trunk encapsulation: dot1q
Administrative private-vlan trunk normal VLANs: none
Administrative private-vlan trunk associations: none
Administrative private-vlan trunk mappings: none
Operational private-vlan: none
Trunking VLANs Enabled: ALL
Pruning VLANs Enabled: 2-1001
Capture Mode Disabled
Capture VLANs Allowed: ALL
Protected: false
Unknown unicast blocked: disabled
Unknown multicast blocked: disabled
Appliance trust: none
Switch_2#
Switch_2#
Switch_2#
Switch_2#conf t
Enter configuration commands, one per line. End with CNTL/Z.
Switch_2(config)#int gi 0/1
Switch_2(config-if)#switchport trunk encapsulation dot
Switch_2(config-if)#switchport mode dynamic auto
Switch_2(config-if)#exit
Switch_2(config)#exit
Switch_2#
Switch_2#
Switch_2#
*Mar 1 01:09:48.222: %SYS-5-CONFIG_I: Configured from console by console
Switch_2#
Switch_2#
Switch_2#
Switch_2#sh int gi 0/1 swit
Name: Gi0/1
Switchport: Enabled
Administrative Mode: dynamic auto
Operational Mode: static access
Administrative Trunking Encapsulation: dot1q
Operational Trunking Encapsulation: native
Negotiation of Trunking: On
Access Mode VLAN: 1 (default)
Trunking Native Mode VLAN: 1 (default)
Administrative Native VLAN tagging: enabled
Voice VLAN: none
Administrative private-vlan host-association: none
Administrative private-vlan mapping: none
Administrative private-vlan trunk native VLAN: none
Administrative private-vlan trunk Native VLAN tagging: enabled
Administrative private-vlan trunk encapsulation: dot1q
Administrative private-vlan trunk normal VLANs: none
Administrative private-vlan trunk associations: none
Administrative private-vlan trunk mappings: none
Operational private-vlan: none
Trunking VLANs Enabled: ALL
Pruning VLANs Enabled: 2-1001
Capture Mode Disabled
Capture VLANs Allowed: ALL
Protected: false
Unknown unicast blocked: disabled
Unknown multicast blocked: disabled
Appliance trust: none
Switch_2#
Switch_2#
Switch_2#
Switch_2#sh int trun
Switch_2#sh int trun
Switch_2#
====================================================================
= Testing one side Auto, one side Desirable
====================================================================
changing int gi 0/1 to desirable
Switch_2#
Switch_2#
Switch_2#conf t
Enter configuration commands, one per line. End with CNTL/Z.
Switch_2(config)#int gi 0/1
Switch_2(config-if)#switchport mode dynamic desirable
Switch_2(config-if)#exit
Switch_2(config)#exit
Switch_2#
*Mar 1 01:13:52.733: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/1, changed state to down
*Mar 1 01:13:53.630: %SYS-5-CONFIG_I: Configured from console by console
*Mar 1 01:13:55.753: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/1, changed state to up
Switch_2#
Switch_2#
Switch_2#sh int trunk
Port Mode Encapsulation Status Native vlan
Gi0/1 desirable 802.1q trunking 1
Port Vlans allowed on trunk
Gi0/1 1-4094
Port Vlans allowed and active in management domain
Gi0/1 1
Port Vlans in spanning tree forwarding state and not pruned
Gi0/1 none
Switch_2#
Switch_2#
Switch_2#
Switch_2#sh int gi 0/1 swit
Name: Gi0/1
Switchport: Enabled
Administrative Mode: dynamic desirable
Operational Mode: trunk
Administrative Trunking Encapsulation: dot1q
Operational Trunking Encapsulation: dot1q
Negotiation of Trunking: On
Access Mode VLAN: 1 (default)
Trunking Native Mode VLAN: 1 (default)
Administrative Native VLAN tagging: enabled
Voice VLAN: none
Administrative private-vlan host-association: none
Administrative private-vlan mapping: none
Administrative private-vlan trunk native VLAN: none
Administrative private-vlan trunk Native VLAN tagging: enabled
Administrative private-vlan trunk encapsulation: dot1q
Administrative private-vlan trunk normal VLANs: none
Administrative private-vlan trunk associations: none
Administrative private-vlan trunk mappings: none
Operational private-vlan: none
Trunking VLANs Enabled: ALL
Pruning VLANs Enabled: 2-1001
Capture Mode Disabled
Capture VLANs Allowed: ALL
Protected: false
Unknown unicast blocked: disabled
Unknown multicast blocked: disabled
Appliance trust: none
Switch_2#
—————
checking switch 1
Switch_1#
Switch_1#
Switch_1#sh int trunk
Port Mode Encapsulation Status Native vlan
Gi0/1 auto n-802.1q trunking 1
Switch_1#
Switch_1#
Switch_1#
Switch_1#sh int gi 0/1 switch
Name: Gi0/1
Switchport: Enabled
Administrative Mode: dynamic auto
Operational Mode: trunk
Administrative Trunking Encapsulation: negotiate
Operational Trunking Encapsulation: dot1q
Negotiation of Trunking: On
Access Mode VLAN: 1 (default)
Trunking Native Mode VLAN: 1 (default)
Administrative Native VLAN tagging: enabled
Voice VLAN: none
Administrative private-vlan host-association: none
Administrative private-vlan mapping: none
Administrative private-vlan trunk native VLAN: none
Administrative private-vlan trunk Native VLAN tagging: enabled
Administrative private-vlan trunk encapsulation: dot1q
Administrative private-vlan trunk normal VLANs: none
Administrative private-vlan trunk associations: none
Administrative private-vlan trunk mappings: none
Operational private-vlan: none
Trunking VLANs Enabled: ALL
Pruning VLANs Enabled: 2-1001
Capture Mode Disabled
Capture VLANs Allowed: ALL
Protected: false
Unknown unicast blocked: disabled
Unknown multicast blocked: disabled
Appliance trust: none
Switch_1#
=====================================================
= Testing both sides desirable
=====================================================
changing switch 1 to be desirable
Switch_1#
Switch_1#sh int trunk
Port Mode Encapsulation Status Native vlan
Gi0/1 auto n-802.1q trunking 1
Port Vlans allowed on trunk
Gi0/1 1-4094
Port Vlans allowed and active in management domain
Gi0/1 1
Port Vlans in spanning tree forwarding state and not pruned
Gi0/1 1
Switch_1#
Switch_1#
Switch_1#
Switch_1#sh int gi 0/1 switch
Name: Gi0/1
Switchport: Enabled
Administrative Mode: dynamic auto
Operational Mode: trunk
Administrative Trunking Encapsulation: negotiate
Operational Trunking Encapsulation: dot1q
Negotiation of Trunking: On
Access Mode VLAN: 1 (default)
Trunking Native Mode VLAN: 1 (default)
Administrative Native VLAN tagging: enabled
Voice VLAN: none
Administrative private-vlan host-association: none
Administrative private-vlan mapping: none
Administrative private-vlan trunk native VLAN: none
Administrative private-vlan trunk Native VLAN tagging: enabled
Administrative private-vlan trunk encapsulation: dot1q
Administrative private-vlan trunk normal VLANs: none
Administrative private-vlan trunk associations: none
Administrative private-vlan trunk mappings: none
Operational private-vlan: none
Trunking VLANs Enabled: ALL
Pruning VLANs Enabled: 2-1001
Capture Mode Disabled
Capture VLANs Allowed: ALL
Protected: false
Unknown unicast blocked: disabled
Unknown multicast blocked: disabled
Appliance trust: none
Switch_1#
Switch_1#
Switch_1#
Switch_1#sh run int gi 0/1
Building configuration…
Current configuration : 36 bytes
!
interface GigabitEthernet0/1
end
Switch_1#
Switch_1#
Switch_1#
Switch_1#conf t
Enter configuration commands, one per line. End with CNTL/Z.
Switch_1(config)#int gi 0/1
Switch_1(config-if)#switchport trunk encap dot
Switch_1(config-if)#switchport mode dynamic desirable
Switch_1(config-if)#exit
Switch_1(config)#exit
Switch_1#
*Mar 12 17:41:44.689: %SYS-5-CONFIG_I: Configured from console by console
Switch_1#
Switch_1#
Switch_1#sh int trunk
Port Mode Encapsulation Status Native vlan
Gi0/1 desirable 802.1q trunking 1
Port Vlans allowed on trunk
Gi0/1 1-4094
Port Vlans allowed and active in management domain
Gi0/1 1
Port Vlans in spanning tree forwarding state and not pruned
Gi0/1 1
Switch_1#
Switch_1#
Switch_1#sh int gi 0/1 swit
Name: Gi0/1
Switchport: Enabled
Administrative Mode: dynamic desirable
Operational Mode: trunk
Administrative Trunking Encapsulation: dot1q
Operational Trunking Encapsulation: dot1q
Negotiation of Trunking: On
Access Mode VLAN: 1 (default)
Trunking Native Mode VLAN: 1 (default)
Administrative Native VLAN tagging: enabled
Voice VLAN: none
Administrative private-vlan host-association: none
Administrative private-vlan mapping: none
Administrative private-vlan trunk native VLAN: none
Administrative private-vlan trunk Native VLAN tagging: enabled
Administrative private-vlan trunk encapsulation: dot1q
Administrative private-vlan trunk normal VLANs: none
Administrative private-vlan trunk associations: none
Administrative private-vlan trunk mappings: none
Operational private-vlan: none
Trunking VLANs Enabled: ALL
Pruning VLANs Enabled: 2-1001
Capture Mode Disabled
Capture VLANs Allowed: ALL
Protected: false
Unknown unicast blocked: disabled
Unknown multicast blocked: disabled
Appliance trust: none
Switch_1#
=================================================
= Both sides desirable test
==================================================
Switch_1#
Switch_1#
Switch_1#
Switch_1#
Switch_1#sh int trunk
Port Mode Encapsulation Status Native vlan
Gi0/1 desirable 802.1q trunking 1
Port Vlans allowed on trunk
Gi0/1 1-4094
Port Vlans allowed and active in management domain
Gi0/1 1
Port Vlans in spanning tree forwarding state and not pruned
Gi0/1 1
Switch_1#sh int gi 0/1 swit
Name: Gi0/1
Switchport: Enabled
Administrative Mode: dynamic desirable
Operational Mode: trunk
Administrative Trunking Encapsulation: dot1q
Operational Trunking Encapsulation: dot1q
Negotiation of Trunking: On
Access Mode VLAN: 1 (default)
Trunking Native Mode VLAN: 1 (default)
Administrative Native VLAN tagging: enabled
Voice VLAN: none
Administrative private-vlan host-association: none
Administrative private-vlan mapping: none
Administrative private-vlan trunk native VLAN: none
Administrative private-vlan trunk Native VLAN tagging: enabled
Administrative private-vlan trunk encapsulation: dot1q
Administrative private-vlan trunk normal VLANs: none
Administrative private-vlan trunk associations: none
Administrative private-vlan trunk mappings: none
Operational private-vlan: none
Trunking VLANs Enabled: ALL
Pruning VLANs Enabled: 2-1001
Capture Mode Disabled
Capture VLANs Allowed: ALL
Protected: false
Unknown unicast blocked: disabled
Unknown multicast blocked: disabled
Appliance trust: none
Switch_1#
Switch_1#
Switch_2#
Switch_2#
Switch_2#
Switch_2#
Switch_2#sh int trunk
Port Mode Encapsulation Status Native vlan
Gi0/1 desirable 802.1q trunking 1
Port Vlans allowed on trunk
Gi0/1 1-4094
Port Vlans allowed and active in management domain
Gi0/1 1
Port Vlans in spanning tree forwarding state and not pruned
Gi0/1 1
Switch_2#
Switch_2#
Switch_2#
Switch_2#
Switch_2#sh int gi 0/1 swit
Name: Gi0/1
Switchport: Enabled
Administrative Mode: dynamic desirable
Operational Mode: trunk
Administrative Trunking Encapsulation: dot1q
Operational Trunking Encapsulation: dot1q
Negotiation of Trunking: On
Access Mode VLAN: 1 (default)
Trunking Native Mode VLAN: 1 (default)
Administrative Native VLAN tagging: enabled
Voice VLAN: none
Administrative private-vlan host-association: none
Administrative private-vlan mapping: none
Administrative private-vlan trunk native VLAN: none
Administrative private-vlan trunk Native VLAN tagging: enabled
Administrative private-vlan trunk encapsulation: dot1q
Administrative private-vlan trunk normal VLANs: none
Administrative private-vlan trunk associations: none
Administrative private-vlan trunk mappings: none
Operational private-vlan: none
Trunking VLANs Enabled: ALL
Pruning VLANs Enabled: 2-1001
Capture Mode Disabled
Capture VLANs Allowed: ALL
Protected: false
Unknown unicast blocked: disabled
Unknown multicast blocked: disabled
Appliance trust: none
Switch_2#
Switch_2#
Switch_2#
Switch_2#int gi 0/1
^
% Invalid input detected at ‘^’ marker.
Switch_2#conf t
Enter configuration commands, one per line. End with CNTL/Z.
Switch_2(config)#int gi 0/1
Switch_2(config-if)#shut
Switch_2(config-if)#exit
Switch_2(config)#exit
Switch_2#
Switch_2#
Switch_2#
Switch_2#
*Mar 1 02:09:09.093: %LINK-5-CHANGED: Interface GigabitEthernet0/1, changed state to administratively down
*Mar 1 02:09:09.236: %SYS-5-CONFIG_I: Configured from console by console
*Mar 1 02:09:10.100: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/1, changed state to down
Switch_2#
Switch_2#sh int trunk
Switch_2#
Switch_2#
Switch_2#
Switch_2#
Switch_2#conf t
Enter configuration commands, one per line. End with CNTL/Z.
Switch_2(config)#int gi 0/1
Switch_2(config-if)#no shut
Switch_2(config-if)#exit
Switch_2(config)#exit
Switch_2#
Switch_2#
Switch_2#
*Mar 1 02:09:20.544: %SYS-5-CONFIG_I: Configured from console by console
*Mar 1 02:09:21.433: %LINK-3-UPDOWN: Interface GigabitEthernet0/1, changed state to down
*Mar 1 02:09:23.832: %LINK-3-UPDOWN: Interface GigabitEthernet0/1, changed state to up
*Mar 1 02:09:25.862: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/1, changed state to up
Switch_2#
Switch_2#
Switch_2#sh int trunk
Port Mode Encapsulation Status Native vlan
Gi0/1 desirable 802.1q trunking 1
Port Vlans allowed on trunk
Gi0/1 1-4094
Port Vlans allowed and active in management domain
Gi0/1 1
Port Vlans in spanning tree forwarding state and not pruned
Gi0/1 none
Switch_2#
Switch_1#
Switch_1#sh int trunk
Port Mode Encapsulation Status Native vlan
Gi0/1 desirable 802.1q trunking 1
Port Vlans allowed on trunk
Gi0/1 1-4094
Port Vlans allowed and active in management domain
Gi0/1 1
Port Vlans in spanning tree forwarding state and not pruned
Gi0/1 1
Switch_1#sh int gi 0/1 swit
Name: Gi0/1
Switchport: Enabled
Administrative Mode: dynamic desirable
Operational Mode: trunk
Administrative Trunking Encapsulation: dot1q
Operational Trunking Encapsulation: dot1q
Negotiation of Trunking: On
Access Mode VLAN: 1 (default)
Trunking Native Mode VLAN: 1 (default)
Administrative Native VLAN tagging: enabled
Voice VLAN: none
Administrative private-vlan host-association: none
Administrative private-vlan mapping: none
Administrative private-vlan trunk native VLAN: none
Administrative private-vlan trunk Native VLAN tagging: enabled
Administrative private-vlan trunk encapsulation: dot1q
Administrative private-vlan trunk normal VLANs: none
Administrative private-vlan trunk associations: none
Administrative private-vlan trunk mappings: none
Operational private-vlan: none
Trunking VLANs Enabled: ALL
Pruning VLANs Enabled: 2-1001
Capture Mode Disabled
Capture VLANs Allowed: ALL
Protected: false
Unknown unicast blocked: disabled
Unknown multicast blocked: disabled
Appliance trust: none
Switch_1#
=======================================================================
=both ports now desirable, changing switch 2 to be “auto”.
=======================================================================
Switch_2#
Switch_2#sh int trunk
Port Mode Encapsulation Status Native vlan
Gi0/1 desirable 802.1q trunking 1
Port Vlans allowed on trunk
Gi0/1 1-4094
Port Vlans allowed and active in management domain
Gi0/1 1
Port Vlans in spanning tree forwarding state and not pruned
Gi0/1 1
Switch_2#
Switch_2#
Switch_2#sh int gi 0/1 switch
Name: Gi0/1
Switchport: Enabled
Administrative Mode: dynamic desirable
Operational Mode: trunk
Administrative Trunking Encapsulation: dot1q
Operational Trunking Encapsulation: dot1q
Negotiation of Trunking: On
Access Mode VLAN: 1 (default)
Trunking Native Mode VLAN: 1 (default)
Administrative Native VLAN tagging: enabled
Voice VLAN: none
Administrative private-vlan host-association: none
Administrative private-vlan mapping: none
Administrative private-vlan trunk native VLAN: none
Administrative private-vlan trunk Native VLAN tagging: enabled
Administrative private-vlan trunk encapsulation: dot1q
Administrative private-vlan trunk normal VLANs: none
Administrative private-vlan trunk associations: none
Administrative private-vlan trunk mappings: none
Operational private-vlan: none
Trunking VLANs Enabled: ALL
Pruning VLANs Enabled: 2-1001
Capture Mode Disabled
Capture VLANs Allowed: ALL
Protected: false
Unknown unicast blocked: disabled
Unknown multicast blocked: disabled
Appliance trust: none
Switch_2#
Switch_2#
Switch_2#
Switch_2#conf t
Enter configuration commands, one per line. End with CNTL/Z.
Switch_2(config)#int gi 0/1
Switch_2(config-if)#switchport mode dyn
Switch_2(config-if)#switchport mode dynamic ?
auto Set trunking mode dynamic negotiation parameter to AUTO
desirable Set trunking mode dynamic negotiation parameter to DESIRABLE
Switch_2(config-if)#switchport mode dynamic auto
Switch_2(config-if)#exit
Switch_2(config)#exit
Switch_2#
*Mar 1 01:20:45.385: %SYS-5-CONFIG_I: Configured from console by console
Switch_2#
Switch_2#
Switch_2#
Switch_2#sh int trun
Port Mode Encapsulation Status Native vlan
Gi0/1 auto 802.1q trunking 1
Port Vlans allowed on trunk
Gi0/1 1-4094
Port Vlans allowed and active in management domain
Gi0/1 1
Port Vlans in spanning tree forwarding state and not pruned
Gi0/1 1
Switch_2#
Switch_2#
Switch_2#
Switch_2#
Switch_2#
Switch_2#sh int gi 0/1 switch
Name: Gi0/1
Switchport: Enabled
Administrative Mode: dynamic auto
Operational Mode: trunk
Administrative Trunking Encapsulation: dot1q
Operational Trunking Encapsulation: dot1q
Negotiation of Trunking: On
Access Mode VLAN: 1 (default)
Trunking Native Mode VLAN: 1 (default)
Administrative Native VLAN tagging: enabled
Voice VLAN: none
Administrative private-vlan host-association: none
Administrative private-vlan mapping: none
Administrative private-vlan trunk native VLAN: none
Administrative private-vlan trunk Native VLAN tagging: enabled
Administrative private-vlan trunk encapsulation: dot1q
Administrative private-vlan trunk normal VLANs: none
Administrative private-vlan trunk associations: none
Administrative private-vlan trunk mappings: none
Operational private-vlan: none
Trunking VLANs Enabled: ALL
Pruning VLANs Enabled: 2-1001
Capture Mode Disabled
Capture VLANs Allowed: ALL
Protected: false
Unknown unicast blocked: disabled
Unknown multicast blocked: disabled
Appliance trust: none
Switch_2#
Switch_2#
==========================================================
= Testing Desirable /On
==========================================================
Both sides are desirable/desirable and trunking. Changing one side to ON.
Switch_1#
Switch_1#
Switch_1#
Switch_1#sh int trunk
Port Mode Encapsulation Status Native vlan
Gi0/1 desirable 802.1q trunking 1
Port Vlans allowed on trunk
Gi0/1 1-4094
Port Vlans allowed and active in management domain
Gi0/1 1
Port Vlans in spanning tree forwarding state and not pruned
Gi0/1 1
Switch_1#sh int gi 0/1 swit
Name: Gi0/1
Switchport: Enabled
Administrative Mode: dynamic desirable
Operational Mode: trunk
Administrative Trunking Encapsulation: dot1q
Operational Trunking Encapsulation: dot1q
Negotiation of Trunking: On
Access Mode VLAN: 1 (default)
Trunking Native Mode VLAN: 1 (default)
Administrative Native VLAN tagging: enabled
Voice VLAN: none
Administrative private-vlan host-association: none
Administrative private-vlan mapping: none
Administrative private-vlan trunk native VLAN: none
Administrative private-vlan trunk Native VLAN tagging: enabled
Administrative private-vlan trunk encapsulation: dot1q
Administrative private-vlan trunk normal VLANs: none
Administrative private-vlan trunk associations: none
Administrative private-vlan trunk mappings: none
Operational private-vlan: none
Trunking VLANs Enabled: ALL
Pruning VLANs Enabled: 2-1001
Capture Mode Disabled
Capture VLANs Allowed: ALL
Protected: false
Unknown unicast blocked: disabled
Unknown multicast blocked: disabled
Appliance trust: none
Switch_1#
Switch_1#
Switch_1#
Switch_1#sh run int gi 0/1
Building configuration…
Current configuration : 109 bytes
!
interface GigabitEthernet0/1
switchport trunk encapsulation dot1q
switchport mode dynamic desirable
end
Switch_1#conf t
Enter configuration commands, one per line. End with CNTL/Z.
Switch_1(config)#int gi 0/1
Switch_1(config-if)#switchport mode trunk
Switch_1(config-if)#exit
Switch_1(config)#exit
Switch_1#
Switch_1#
Switch_1#
Switch_1#
Switch_1#
*Mar 12 18:38:29.323: %SYS-5-CONFIG_I: Configured from console by console
Switch_1#
Switch_1#
Switch_1#
Switch_1#sh int trunk
Port Mode Encapsulation Status Native vlan
Gi0/1 on 802.1q trunking 1
Port Vlans allowed on trunk
Gi0/1 1-4094
Port Vlans allowed and active in management domain
Gi0/1 1
Port Vlans in spanning tree forwarding state and not pruned
Gi0/1 1
Switch_1#
Switch_1#
Switch_1#
Switch_1#
Switch_1#conf t
Enter configuration commands, one per line. End with CNTL/Z.
Switch_1(config-if)#switchport non
Switch_1(config-if)#exit
Switch_1(config)#exit
Switch_1#
Switch_1#
Switch_1#
Switch_1#
Switch_1#sh int trunk
*Mar 12 18:39:02.668: %SYS-5-CONFIG_I: Configured from console by console
Port Mode Encapsulation Status Native vlan
Gi0/1 on 802.1q trunking 1
Port Vlans allowed on trunk
Gi0/1 1-4094
Port Vlans allowed and active in management domain
Gi0/1 1
Port Vlans in spanning tree forwarding state and not pruned
Gi0/1 1
Switch_1#
Switch_1#
Switch_1#
Switch_1#
Switch_1#
Switch_1#sh int gi 0/1 switch
Name: Gi0/1
Switchport: Enabled
Administrative Mode: trunk
Operational Mode: trunk
Administrative Trunking Encapsulation: dot1q
Operational Trunking Encapsulation: dot1q
Negotiation of Trunking: Off
Access Mode VLAN: 1 (default)
Trunking Native Mode VLAN: 1 (default)
Administrative Native VLAN tagging: enabled
Voice VLAN: none
Administrative private-vlan host-association: none
Administrative private-vlan mapping: none
Administrative private-vlan trunk native VLAN: none
Administrative private-vlan trunk Native VLAN tagging: enabled
Administrative private-vlan trunk encapsulation: dot1q
Administrative private-vlan trunk normal VLANs: none
Administrative private-vlan trunk associations: none
Administrative private-vlan trunk mappings: none
Operational private-vlan: none
Trunking VLANs Enabled: ALL
Pruning VLANs Enabled: 2-1001
Capture Mode Disabled
Capture VLANs Allowed: ALL
Protected: false
Unknown unicast blocked: disabled
Unknown multicast blocked: disabled
Appliance trust: none
Switch_1#
================================================
= On/On – didn’t test, this would obviously work
================================================
Question 2 testing with live equipment.
******************************************
===============================
= Two switches, connected by Gi0/1
===============================
Switch_1#
Switch_1#sh run int gi 0/1
Building configuration…
Current configuration : 36 bytes
!
interface GigabitEthernet0/1
end
Switch_1#sh int status | i Gi0/1_
Gi0/1 connected 1 a-full a-1000 10/100/1000BaseTX
Switch_1#
Switch_1#sh span
VLAN0001
Spanning tree enabled protocol ieee
Root ID Priority 32769
Address 649e.f307.d780
Cost 4
Port 1 (GigabitEthernet0/1)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 32769 (priority 32768 sys-id-ext 1)
Address 70ca.9bfd.2a00
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 300 sec
Interface Role Sts Cost Prio.Nbr Type
——————- —- — ——— ——– ——————————–
Gi0/1 Root FWD 4 128.1 P2p
Switch_1#
—————
Switch_1#
Switch_1#sh run int gi 0/1
Building configuration…
Current configuration : 36 bytes
!
interface GigabitEthernet0/1
end
Switch_1#sh int status | i Gi0/1_
Gi0/1 connected 1 a-full a-1000 10/100/1000BaseTX
Switch_1#
Switch_2#sh run int gi 0/1
Building configuration…
Current configuration : 36 bytes
!
interface GigabitEthernet0/1
end
Switch_2#sh int status | i Gi0/1_
Gi0/1 connected 1 a-full a-1000 10/100/1000BaseTX
Switch_2#
Switch_2#sh span
VLAN0001
Spanning tree enabled protocol ieee
Root ID Priority 32769
Address 649e.f307.d780
This bridge is the root
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 32769 (priority 32768 sys-id-ext 1)
Address 649e.f307.d780
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 300 sec
Interface Role Sts Cost Prio.Nbr Type
——————- —- — ——— ——– ——————————–
Gi0/1 Desg FWD 4 128.1 P2p
Switch_2#
=======================================================================================
=connecting 2nd connection on Gi0/2 with default config
=======================================================================================
Switch_1#
Switch_1#
1w4d: set portid: VLAN0001 Gi0/2: new port id 8002
1w4d: STP: VLAN0001 Gi0/2 -> listening
1w4d: STP: VLAN0001 Gi0/2 -> blocking
1w4d: %LINK-3-UPDOWN: Interface GigabitEthernet0/2, changed state to up
1w4d: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/2, changed state to up
Switch_1#
Switch_1#
Switch_1#sh span
VLAN0001
Spanning tree enabled protocol ieee
Root ID Priority 32769
Address 649e.f307.d780
Cost 4
Port 1 (GigabitEthernet0/1)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 32769 (priority 32768 sys-id-ext 1)
Address 70ca.9bfd.2a00
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 15 sec
Interface Role Sts Cost Prio.Nbr Type
——————- —- — ——— ——– ——————————–
Gi0/1 Root FWD 4 128.1 P2p
Gi0/2 Altn BLK 4 128.2 P2p
Switch_1#
———————————————————————————
Switch_2#
Switch_2#sh span
VLAN0001
Spanning tree enabled protocol ieee
Root ID Priority 32769
Address 649e.f307.d780
This bridge is the root
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 32769 (priority 32768 sys-id-ext 1)
Address 649e.f307.d780
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 300 sec
Interface Role Sts Cost Prio.Nbr Type
——————- —- — ——— ——– ——————————–
Gi0/1 Desg FWD 4 128.1 P2p
Gi0/2 Desg FWD 4 128.2 P2p
Switch_2#
==============================================================================
= let’s make switch 1 the root, and add vlan 2 to mirror the question topology
==============================================================================
Switch_1#
Switch_1#
Switch_1#conf t
Enter configuration commands, one per line. End with CNTL/Z.
Switch_1(config)#spanning-tree vlan 1-4092 root primary
Switch_1(config)#
1w4d: setting bridge id (which=1) prio 24577 prio cfg 24576 sysid 1 (on) id 6001.70ca.9bfd.2a00
1w4d: STP: VLAN0001 we are the spanning tree root
1w4d: STP: VLAN0001 Gi0/2 -> listening
1w4d: STP: VLAN0001 Topology Change rcvd on Gi0/1
1w4d: STP: VLAN0001 Gi0/2 -> learning
1w4d: STP: VLAN0001 Gi0/2 -> forwarding
Switch_1(config)#
Switch_1(config)#
Switch_1(config)#vlan 2
Switch_1(config-vlan)#exit
Switch_1(config)#do sh vlan
VLAN Name Status Ports
—- ——————————– ——— ——————————-
1 default active Gi0/1, Gi0/2, Gi0/3, Gi0/4
Gi0/5, Gi0/6, Gi0/7, Gi0/8
Gi0/9, Gi0/10, Gi0/11, Gi0/12
Gi0/13, Gi0/14, Gi0/15, Gi0/16
Gi0/17, Gi0/18
Gi0/21, Gi0/22, Gi0/23, Gi0/24
Gi0/25, Gi0/26, Gi0/27, Gi0/28
Gi0/29, Gi0/30, Gi0/31, Gi0/32
Gi0/33, Gi0/34, Gi0/35, Gi0/36
Gi0/37, Gi0/38, Gi0/39, Gi0/40
Gi0/41, Gi0/42, Gi0/43, Gi0/44
Gi0/45, Gi0/46, Gi0/47, Gi0/48
Gi1/1, Gi1/2, Gi1/3, Gi1/4
2 VLAN0002 active
1002 fddi-default act/unsup
1003 token-ring-default act/unsup
1004 fddinet-default act/unsup
1005 trnet-default act/unsup
VLAN Type SAID MTU Parent RingNo BridgeNo Stp BrdgMode Trans1 Trans2
Switch_1(config)#
———————————–
set up trunking by making Gi0/1 and Gi0/2 desirable.
————–
Switch_1#
Switch_1#conf t
Enter configuration commands, one per line. End with CNTL/Z.
Switch_1(config)#int range gi 0/1 – 2
Switch_1(config-if-range)#switchport trunk encapsulation dot
Switch_1(config-if-range)#switchport mode dynamic des
Switch_1(config-if-range)#exit
Switch_1(config)#
DEBUGS:
1w4d: STP[1]: Generating TC trap for port GigabitEthernet0/1
1w4d: STP[1]: Generating TC trap for port GigabitEthernet0/2
1w4d: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/1, changed state to down
1w4d: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/2, changed state to down
1w4d: setting bridge id (which=3) prio 24577 prio cfg 24576 sysid 1 (on) id 6001.70ca.9bfd.2a00
1w4d: set portid: VLAN0001 Gi0/1: new port id 8001
1w4d: STP: VLAN0001 Gi0/1 -> listening
1w4d: setting bridge id (which=3) prio 24578 prio cfg 24576 sysid 2 (on) id 6002.70ca.9bfd.2a00
1w4d: set portid: VLAN0002 Gi0/1: new port id 8001
1w4d: STP: VLAN0002 Gi0/1 -> listening
1w4d: set portid: VLAN0001 Gi0/2: new port id 8002
1w4d: STP: VLAN0001 Gi0/2 -> listening
1w4d: set portid: VLAN0002 Gi0/2: new port id 8002
1w4d: STP: VLAN0002 Gi0/2 -> listening
1w4d: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/1, changed state to up
1w4d: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/2, changed state to up
1w4d: STP: VLAN0001 heard root 32769-649e.f307.d780 on Gi0/1
1w4d: STP: VLAN0001 heard root 32769-649e.f307.d780 on Gi0/2
1w4d: STP: VLAN0001 Gi0/1 -> learning
1w4d: STP: VLAN0002 Gi0/1 -> learning
1w4d: STP: VLAN0001 Gi0/2 -> learning
1w4d: STP: VLAN0002 Gi0/2 -> learning
1w4d: STP[1]: Generating TC trap for port GigabitEthernet0/1
1w4d: STP: VLAN0001 Gi0/1 -> forwarding
1w4d: STP[2]: Generating TC trap for port GigabitEthernet0/1
1w4d: STP: VLAN0002 Gi0/1 -> forwarding
1w4d: STP[1]: Generating TC trap for port GigabitEthernet0/2
1w4d: STP: VLAN0001 Gi0/2 -> forwarding
1w4d: STP[2]: Generating TC trap for port GigabitEthernet0/2
1w4d: STP: VLAN0002 Gi0/2 -> forwarding
Switch_1(config)#
Switch_1#sh span
VLAN0001
Spanning tree enabled protocol ieee
Root ID Priority 24577
Address 70ca.9bfd.2a00
This bridge is the root
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 24577 (priority 24576 sys-id-ext 1)
Address 70ca.9bfd.2a00
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 300 sec
Interface Role Sts Cost Prio.Nbr Type
——————- —- — ——— ——– ——————————–
Gi0/1 Desg FWD 4 128.1 P2p
Gi0/2 Desg FWD 4 128.2 P2p
VLAN0002
Spanning tree enabled protocol ieee
Root ID Priority 24578
Address 70ca.9bfd.2a00
This bridge is the root
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 24578 (priority 24576 sys-id-ext 2)
Address 70ca.9bfd.2a00
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 300 sec
Interface Role Sts Cost Prio.Nbr Type
——————- —- — ——— ——– ——————————–
Gi0/1 Desg FWD 4 128.1 P2p
Gi0/2 Desg FWD 4 128.2 P2p
Switch_2#sh span
VLAN0001
Spanning tree enabled protocol ieee
Root ID Priority 24577
Address 70ca.9bfd.2a00
Cost 4
Port 1 (GigabitEthernet0/1)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 32769 (priority 32768 sys-id-ext 1)
Address 649e.f307.d780
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 300 sec
Interface Role Sts Cost Prio.Nbr Type
——————- —- — ——— ——– ——————————–
Gi0/1 Root FWD 4 128.1 P2p
Gi0/2 Altn BLK 4 128.2 P2p
VLAN0002
Spanning tree enabled protocol ieee
Root ID Priority 24578
Address 70ca.9bfd.2a00
Cost 4
Port 1 (GigabitEthernet0/1)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 32770 (priority 32768 sys-id-ext 2)
Address 649e.f307.d780
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 300 sec
Interface Role Sts Cost Prio.Nbr Type
——————- —- — ——— ——– ——————————–
Gi0/1 Root LIS 4 128.1 P2p
Gi0/2 Altn BLK 4 128.2 P2p
===========================================================================================
= Topology is now as Question 2 – port D2 (Switch2, Gi0/2) is blocking.
===========================================================================================
============================================================================================
= Test A. Increase root bridge priority on D for VLAN2 so D2 becomes root for Vlan2 (Switch_2,
port Gi0/2
============================================================================================
Switch_2>en
Switch_2#conf t
Enter configuration commands, one per line. End with CNTL/Z.
Switch_2(config)#spanning-tree vlan 2 root primary
03:06:51: setting bridge id (which=1) prio 24578 prio cfg 24576 sysid 2 (on) id
6002.649e.f307.d780
03:06:51: STP: VLAN0002 we are the spanning tree root
03:06:51: STP: VLAN0002 Gi0/2 -> listening
03:06:51: STP: VLAN0002 Topology Change rcvd on Gi0/1
Switch_2#
03:06:54: %SYS-5-CONFIG_I: Configured from console by console
Switch_2#
03:07:06: STP: VLAN0002 Gi0/2 -> learning
03:07:21: STP: VLAN0002 Gi0/2 -> forwarding
Switch_2#
Switch_2#
Switch_2#
Switch_2#sh span
VLAN0001
Spanning tree enabled protocol ieee
Root ID Priority 24577
Address 70ca.9bfd.2a00
Cost 4
Port 1 (GigabitEthernet0/1)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 32769 (priority 32768 sys-id-ext 1)
Address 649e.f307.d780
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 300 sec
Interface Role Sts Cost Prio.Nbr Type
——————- —- — ——— ——– ——————————–
Gi0/1 Root FWD 4 128.1 P2p
Gi0/2 Altn BLK 4 128.2 P2p
VLAN0002
Spanning tree enabled protocol ieee
Root ID Priority 24578
Address 649e.f307.d780
This bridge is the root
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 24578 (priority 24576 sys-id-ext 2)
Address 649e.f307.d780
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 15 sec
Interface Role Sts Cost Prio.Nbr Type
——————- —- — ——— ——– ——————————–
Gi0/1 Desg FWD 4 128.1 P2p
Gi0/2 Desg FWD 4 128.2 P2p
Switch_2#
======================================================================
= Test A Result: port Gi0/2 became a DESIGNATED port, not a ROOT port. Switch_2 (D) is the root
for vlan 2 – with the command spannint-tree vlan 2 root primary.
Technically, A is wrong. The port became designated, not root. Also, this is not the “easist
way” since this involved suspending spanning tree for vlan 2 while STP reconverged with a new
root
======================================================================
======================================================================
= Test B: – Decrease the port priority on R2 (Switch_1, Gi0/2) for VLAN2 on CatR (Switch_1) so
that port D1 (Switch_2 Gi0/1) will be blocked for Vlan2 and port D2 (Switch_2 Gi0/2) will remain
blocked for vlan 1.
======================================================================
Switch_1#
Switch_1#sh span
VLAN0001
Spanning tree enabled protocol ieee
Root ID Priority 24577
Address 70ca.9bfd.2a00
This bridge is the root
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 24577 (priority 24576 sys-id-ext 1)
Address 70ca.9bfd.2a00
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 300 sec
Interface Role Sts Cost Prio.Nbr Type
——————- —- — ——— ——– ——————————–
Gi0/1 Desg FWD 4 128.1 P2p
Gi0/2 Desg FWD 4 128.2 P2p
VLAN0002
Spanning tree enabled protocol ieee
Root ID Priority 24578
Address 70ca.9bfd.2a00
This bridge is the root
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 24578 (priority 24576 sys-id-ext 2)
Address 70ca.9bfd.2a00
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 300 sec
Interface Role Sts Cost Prio.Nbr Type
——————- —- — ——— ——– ——————————–
Gi0/1 Desg FWD 4 128.1 P2p
Gi0/2 Desg FWD 4 128.2 P2p
Switch_1#sh run int gi 0/2
Building configuration…
Current configuration : 109 bytes
!
interface GigabitEthernet0/2
switchport trunk encapsulation dot1q
switchport mode dynamic desirable
end
Switch_1#conf t
Enter configuration commands, one per line. End with CNTL/Z.
Switch_1(config)#int gi 0/2
Switch_1(config-if)#spanning-tree vlan 2 port-priority 16
Switch_1(config-if)#exit
1w4d: set portid: VLAN0002 Gi0/2: new port id 1002
Switch_1(config)#exit
Switch_1#
1w4d: STP: VLAN0002 Topology Change rcvd on Gi0/2
1w4d: %SYS-5-CONFIG_I: Configured from console by console
Switch_1#exit
Switch_1#sh span
VLAN0001
Spanning tree enabled protocol ieee
Root ID Priority 24577
Address 70ca.9bfd.2a00
This bridge is the root
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 24577 (priority 24576 sys-id-ext 1)
Address 70ca.9bfd.2a00
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 300 sec
Interface Role Sts Cost Prio.Nbr Type
——————- —- — ——— ——– ——————————–
Gi0/1 Desg FWD 4 128.1 P2p
Gi0/2 Desg FWD 4 128.2 P2p
VLAN0002
Spanning tree enabled protocol ieee
Root ID Priority 24578
Address 70ca.9bfd.2a00
This bridge is the root
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 24578 (priority 24576 sys-id-ext 2)
Address 70ca.9bfd.2a00
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 15 sec
Interface Role Sts Cost Prio.Nbr Type
——————- —- — ——— ——– ——————————–
Gi0/1 Desg FWD 4 128.1 P2p
Gi0/2 Desg FWD 4 16.2 P2p
Switch_1#
Switch_2#sh span
VLAN0001
Spanning tree enabled protocol ieee
Root ID Priority 24577
Address 70ca.9bfd.2a00
Cost 4
Port 1 (GigabitEthernet0/1)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 32769 (priority 32768 sys-id-ext 1)
Address 649e.f307.d780
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 300 sec
Interface Role Sts Cost Prio.Nbr Type
——————- —- — ——— ——– ——————————–
Gi0/1 Root FWD 4 128.1 P2p
Gi0/2 Altn BLK 4 128.2 P2p
VLAN0002
Spanning tree enabled protocol ieee
Root ID Priority 24578
Address 70ca.9bfd.2a00
Cost 4
Port 2 (GigabitEthernet0/2)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 32770 (priority 32768 sys-id-ext 2)
Address 649e.f307.d780
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 300 sec
Interface Role Sts Cost Prio.Nbr Type
——————- —- — ——— ——– ——————————–
Gi0/1 Altn BLK 4 128.1 P2p
Gi0/2 Root FWD 4 128.2 P2p
Switch_2#
===================================================================================
= Test B results – THIS WORKED – Port D1 (Switch_2 Gi0/1) is blocked for Vlan2, and port D2
(Switch_2 Gi 0/2) remained blocked for vlan 1.
===================================================================================
===================================================================================
=Test C: Decrease the path cost on R2 on Catalyst R for VLAN 2 so that port D1 will be blocked
for VLAN 2 and port D2 will remain blocked for VLAN 1.
===================================================================================
Switch_1#sh span
VLAN0001
Spanning tree enabled protocol ieee
Root ID Priority 24577
Address 70ca.9bfd.2a00
This bridge is the root
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 24577 (priority 24576 sys-id-ext 1)
Address 70ca.9bfd.2a00
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 300 sec
Interface Role Sts Cost Prio.Nbr Type
——————- —- — ——— ——– ——————————–
Gi0/1 Desg FWD 4 128.1 P2p
Gi0/2 Desg FWD 4 128.2 P2p
VLAN0002
Spanning tree enabled protocol ieee
Root ID Priority 24578
Address 70ca.9bfd.2a00
This bridge is the root
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 24578 (priority 24576 sys-id-ext 2)
Address 70ca.9bfd.2a00
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 300 sec
Interface Role Sts Cost Prio.Nbr Type
——————- —- — ——— ——– ——————————–
Gi0/1 Desg FWD 4 128.1 P2p
Gi0/2 Desg FWD 4 128.2 P2p
Switch_2# sh span
VLAN0001
Spanning tree enabled protocol ieee
Root ID Priority 24577
Address 70ca.9bfd.2a00
Cost 4
Port 1 (GigabitEthernet0/1)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 32769 (priority 32768 sys-id-ext 1)
Address 649e.f307.d780
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 300 sec
Interface Role Sts Cost Prio.Nbr Type
——————- —- — ——— ——– ——————————–
Gi0/1 Root FWD 4 128.1 P2p
Gi0/2 Altn BLK 4 128.2 P2p
VLAN0002
Spanning tree enabled protocol ieee
Root ID Priority 24578
Address 70ca.9bfd.2a00
Cost 4
Port 1 (GigabitEthernet0/1)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 32770 (priority 32768 sys-id-ext 2)
Address 649e.f307.d780
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 300 sec
Interface Role Sts Cost Prio.Nbr Type
——————- —- — ——— ——– ——————————–
Gi0/1 Root FWD 4 128.1 P2p
Gi0/2 Altn BLK 4 128.2 P2p
———————————————————————————–
Changing the path cost
———————————————————————————–
Switch_1#conf t
Switch_1(config-if)#spanning-tree vlan 2 cost 1
Switch_1(config-if)#exit
Switch_1(config)#exit
Switch_1#
Switch_1#sh span
VLAN0001
Spanning tree enabled protocol ieee
Root ID Priority 24577
Address 70ca.9bfd.2a00
This bridge is the root
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 24577 (priority 24576 sys-id-ext 1)
Address 70ca.9bfd.2a00
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 300 sec
Interface Role Sts Cost Prio.Nbr Type
——————- —- — ——— ——– ——————————–
Gi0/1 Desg FWD 4 128.1 P2p
Gi0/2 Desg FWD 4 128.2 P2p
VLAN0002
Spanning tree enabled protocol ieee
Root ID Priority 24578
Address 70ca.9bfd.2a00
This bridge is the root
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 24578 (priority 24576 sys-id-ext 2)
Address 70ca.9bfd.2a00
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 300 sec
Interface Role Sts Cost Prio.Nbr Type
——————- —- — ——— ——– ——————————–
Gi0/1 Desg FWD 4 128.1 P2p
Gi0/2 Desg FWD 1 128.2 P2p
Switch_2#
Switch_2#sh span
VLAN0001
Spanning tree enabled protocol ieee
Root ID Priority 24577
Address 70ca.9bfd.2a00
Cost 4
Port 1 (GigabitEthernet0/1)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 32769 (priority 32768 sys-id-ext 1)
Address 649e.f307.d780
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 300 sec
Interface Role Sts Cost Prio.Nbr Type
——————- —- — ——— ——– ——————————–
Gi0/1 Root FWD 4 128.1 P2p
Gi0/2 Altn BLK 4 128.2 P2p
VLAN0002
Spanning tree enabled protocol ieee
Root ID Priority 24578
Address 70ca.9bfd.2a00
Cost 4
Port 1 (GigabitEthernet0/1)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 32770 (priority 32768 sys-id-ext 2)
Address 649e.f307.d780
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 300 sec
Interface Role Sts Cost Prio.Nbr Type
——————- —- — ——— ——– ——————————–
Gi0/1 Root FWD 4 128.1 P2p
Gi0/2 Altn BLK 4 128.2 P2p
Switch_2#
=================================================================================
= Test C Result: This had no effect on the blocking on port D1 or D2
=================================================================================
=================================================================================
= Test D: Increase the root bridge priority (decreasing the numerical priority number) for VLAN
2 on Catalyst R so that R2 becomes the root port on Catalyst D for VLAN 2.
=================================================================================
Switch_1#sh span
1w4d: %SYS-5-CONFIG_I: Configured from console by console
VLAN0001
Spanning tree enabled protocol ieee
Root ID Priority 24577
Address 70ca.9bfd.2a00
This bridge is the root
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 24577 (priority 24576 sys-id-ext 1)
Address 70ca.9bfd.2a00
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 300 sec
Interface Role Sts Cost Prio.Nbr Type
——————- —- — ——— ——– ——————————–
Gi0/1 Desg FWD 4 128.1 P2p
Gi0/2 Desg FWD 4 128.2 P2p
VLAN0002
Spanning tree enabled protocol ieee
Root ID Priority 24578
Address 70ca.9bfd.2a00
This bridge is the root
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 24578 (priority 24576 sys-id-ext 2)
Address 70ca.9bfd.2a00
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 300 sec
Interface Role Sts Cost Prio.Nbr Type
——————- —- — ——— ——– ——————————–
Gi0/1 Desg FWD 4 128.1 P2p
Gi0/2 Desg FWD 4 128.2 P2p
Switch_1#en
Switch_1(config)#spanning-tree vlan 2 priority 4096
Switch_1(config)#exit
Switch_1#exi
1w4d: setting bridge id (which=1) prio 4098 prio cfg 4096 sysid 2 (on) id 1002.70ca.9bfd.2a00t
switch_1#
Switch_1#
Switch_1#sh spann
VLAN0001
Spanning tree enabled protocol ieee
Root ID Priority 24577
Address 70ca.9bfd.2a00
This bridge is the root
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 24577 (priority 24576 sys-id-ext 1)
Address 70ca.9bfd.2a00
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 300 sec
Interface Role Sts Cost Prio.Nbr Type
——————- —- — ——— ——– ——————————–
Gi0/1 Desg FWD 4 128.1 P2p
Gi0/2 Desg FWD 4 128.2 P2p
VLAN0002
Spanning tree enabled protocol ieee
Root ID Priority 4098
Address 70ca.9bfd.2a00
This bridge is the root
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 4098 (priority 4096 sys-id-ext 2)
Address 70ca.9bfd.2a00
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 300 sec
Interface Role Sts Cost Prio.Nbr Type
——————- —- — ——— ——– ——————————–
Gi0/1 Desg FWD 4 128.1 P2p
Gi0/2 Desg FWD 4 128.2 P2p
Switch_1#
Switch_2#sh span
VLAN0001
Spanning tree enabled protocol ieee
Root ID Priority 24577
Address 70ca.9bfd.2a00
Cost 4
Port 1 (GigabitEthernet0/1)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 32769 (priority 32768 sys-id-ext 1)
Address 649e.f307.d780
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 300 sec
Interface Role Sts Cost Prio.Nbr Type
——————- —- — ——— ——– ——————————–
Gi0/1 Root FWD 4 128.1 P2p
Gi0/2 Altn BLK 4 128.2 P2p
VLAN0002
Spanning tree enabled protocol ieee
Root ID Priority 4098
Address 70ca.9bfd.2a00
Cost 4
Port 1 (GigabitEthernet0/1)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 32770 (priority 32768 sys-id-ext 2)
Address 649e.f307.d780
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 300 sec
Interface Role Sts Cost Prio.Nbr Type
——————- —- — ——— ——– ——————————–
Gi0/1 Root FWD 4 128.1 P2p
Gi0/2 Altn BLK 4 128.2 P2p
Switch_2#
================================================================================
= Test Results for D: I think this answer is written incorrectly. Catalyst R (switch_1) is
already the root brigde per, “Catalyst R is the root bridge for both VLAN 1 and VLAN 2”.
Nevertheless, I went ahead with this test, and it had no effect.
=================================================================================
=============================================================================================
=Final Results – B worked as described. A achieved the desired effect, but not as described.
Also, I contend, messing with your root bridges isn’t the easiest way.
=============================================================================================
for Q3,
B can’t be the answer unless one of the 2 switches has no neg.
C cannot be the answer unless it is configured on with no negotiate.
Explanation for C:
if the other end is desirable and trunk did’t come up , the switch1 is not auto nor desirable nor on with negotiate, it has to off or on with no negotiate. and not off because it worked in lab so it has to be on with no negotiate.
trunk won’t form in those cases
1. auto – auto
2. on+dtp off – auto
3. on+dtp off – desirable
Leaves us with A,C,E
Q3. suppose you find more than three right answers. herewith some explanation that might could help.
D is deadly wrong, VTP has no dependency to CDP.
F is also wrong. it is about dot1q trunking tested in LAB, moreover is there a switch without dot1q support?
leaves us with A,B,C,E well actually they all could be true.
E is true. VTP domain mismatch does influence dynamic trunking.
How about A? A is also true. imagine all switches in lab don’t use DTP. and in live network all existing switches use DTP,trunk won’t come up. And how about B and C is the other end on live network? than we have four answers.
But the trick is only three of them must be true. than it must be something in our visualisation (imagination) that needs to be tweaked. how about DTP is on lab, and no DTP is in live network and the other end mention is switches in lab? than it must be only B,C and E true.
So, always had better visualisation on scenario when answering questions guys. hope it helps.
Q3. I think correct answer are A, C, E, with Switch1 set to
switchport mode trunk
switchport nonegotiate
In the laboratory the other end is
switchport mode trunk
switchport nonogotiate
so trunk configuration worked fine. But when network administrator try to add Switch1 to the network, trunk don’t work because the other end is:
switchport mode dynamic desirable
A. The trunking configuration mode on Switch1 is set to Off –> correct, with Switch1 mode on and nonegotiate and the other end dynamic desirable
B. The trunking configuration mode on the other end is set to On –> not correct. This answer could be correct if it says” The trunking configuration mode on the other end is set to On and nonegotiate”, but without nonegotiate this answer is not correct and if it’s correct then answer C is not correct
C. The trunking configuration mode on the other end is set to Desirable. –> correct
D. Cisco Discovery Protocol is not running on the other end. –> not correct
E. There is a VTP domain name mismatch. –> correct
F. Switch1 does not support 802.1Q. –> not correct
Hi Aaron ,good job with CSM.I have a strange behaoivr with sync of 3 pair of csm :2 of them works fine in two different chassis in same site2 of them remain out-of-sync in the same chassis2 of them remain out-sync in two different site ( DWDM 10G connection )All of theme have the same supervisor and csm microcodethe failing CSM message are:Nov 5 16:17:37.086: %CSM_SLB-6-REDUNDANCY_INFO: Module 5 FT info: Active: Bulk sync startedNov 5 16:17:37.094: %CSM_SLB-6-REDUNDANCY_INFO: Module 5 FT info: Active: Sending configurations to Standby CSM, this may take several minutes!Nov 5 16:17:37.098: %CSM_SLB-6-REDUNDANCY_INFO: Module 5 FT info: Active: Sending configuration to Standby CSMNov 5 16:18:37.142: %CSM_SLB-3-REDUNDANCY: Module 5 FT error: Active: Manual bulk sync timed outNov 5 16:18:37.142: %CSM_SLB-3-REDUNDANCY: Module 5 FT error: FT CONFIG SYNC: Failed config sync entity sendbut not timeout appear on local link and on DWDM linkThanks for coop
Q3 – Correct should be C, E, F
A. The trunking configuration mode on Switch1 is set to Off.
Incorrect – If Sw1 is set to oFF trunk would never form/work in LAB
B. The trunking configuration mode on the other end is set to On.
Incorrect – With one end sw at ON mode & other at any ON/AUTO/DESIRABLE/ON with noneg. Only case its doesn’t form is if SW1 was set to OFF mode. But thats not possible or it would have never work in LAB.
C. The trunking configuration mode on the other end is set to Desirable.
Correct- Assuming Sw1 is set to any ON with noneg mode & other end is desirable, Trunk will not form.
With Sw1 in ON with noneg trunk would have form in LAN assuming other sw there was in either ON or ON with noneg mode.
Check mode combitnation table at
http://www.cisco.com/en/US/customer/products/hw/switches/ps700/products_tech_note09186a00801429fb.shtml
D. Cisco Discovery Protocol is not running on the other end.
INCORRECT – Trunking is no where related to CDP
E. There is a VTP domain name mismatch.
Correct – VTP domain need to match at either ends. Assuming VTP domain name set on other end SW is different than Sw1
F. Switch1 does not support 802.1Q.
Correct- Assuming other end sw is configured with dot1q & negiotiating with dot1q whereas Sw1 is configured with ISL.
HTH
I’m strongly agree with m@h3n
I think C,E,F is the answer. I think config in lab was … nonegotiate (no DTP) and encapsulation ISL, maybe both ends same way.
So in production environment.
A … wrong … never become trunk because of off
B … wrong –> On / Nonegotiate (switch1) —> TRUNK !
D … totally wrong
C … could be a issue because desirable / nonegotiate + ISL forced never lead the other end to ISL trunk … So –> No trunk
E .. VTP mismatch –> No trunk
F .. Other switch not supporting dot1.q and other switch forced to ISL (switch 1) –> not trunking
Hope this helps
Regards
A. The trunking configuration mode on Switch1 is set to Off –> Remember that SW1 worked in the lab, -> so this is wrong
B. The trunking configuration mode on the other end is set to On –> On mode just don’t work with mode Off, but as mentioned, SW1 couldnot be OFF -> Wrong
C. The trunking configuration mode on the other end is set to Desirable. –> correct
D. Cisco Discovery Protocol is not running on the other end. –> not correct
E. There is a VTP domain name mismatch. –> correct
F. Switch1 does not support 802.1Q. –> Remember that it says SW1 1 work in the lab, not said that work for both dot1Q and ISL -> Correct if SW1 just support ISL but other ends only support dot1Q.
=====> C, E, F
Hows It Going
Very good video Lisa.
Yours Sincerly
There are 5 possible trunking modes for a switch port:
-Auto: this is the default mode. In this mode, a port will become a trunk port if the device the port is connected to is set to the on or desirable mode.
-Desirable: allows the port to become a trunk port if the device the port is connected to is set to the on, desirable, or auto mode;
-On: sets the port to permanent trunking mode.
-Nonegotiate: sets the port to permanent trunking mode without sending Dynamic Trunking
Protocol (DTP)
-Frame Off: sets the port to permanent non-trunking mode
In this case, we can guess the trunking mode of Switch 1 is auto (default mode). When in the laboratory, the trunking mode of the other end is set to On or Desirable so 2 switches can negotiate and the link becomes trunk with no problem. But when plugging to the network, other switches may have the trunking mode set to auto so the 802.1Q trunk is not coming up.Of course these switches need to be in the same VTP domain so that they can talk with each other. When trying to configure a trunk negation with a mismatched VTP domain you will receive the following error %DTP-5-DOMAINMISMATCH: Unable to perform trunk negotiation on port Gig0/1 because of VTP domain mismatch.
A. Increase the root bridge priority (increasing the numerical priority number) for VLAN 2 on Catalyst D so that port D2 becomes the root port on Catalyst D for VLAN 2.
`i think the right answer is A . to load balance is R configure as root bridge for Vlan 1 R1 and R2 are forwarding for Vlan 1. and configure D root bridge for Vlan 2 so D1 and D2 are forwarding for Vlan 2.