OSPF Questions
Here you will find answers to OSPF Questions
Question 1
Which information is carried in an OSPFv3 intra-area-prefix LSA?
A. IPv6 prefixes
B. link-local addresses
C. solicited node multicast addresses
D. IPv6 prefixes and topology information
Answer: A
Explanation
The OSPFv3’s new LSA, the Intra-area Prefix LSA (type 9), handles intra-area network information that was previously included in OSPFv2 type 2 LSAs. It is used in order to advertise one or more IPv6 prefixes. The prefixes are associated with router segment, stub network segment or transit network segment.
Intra-area prefix LSAs (type 9) & Inter-Area-Prefix-LSA (type 3) carry all IPv6 prefix information, which, in IPv4, is included in router LSAs and network LSAs.
Note: An address prefix is represented by three fields: prefix length, prefix options, and address prefix. In OSPFv3, addresses for these LSAs are expressed as prefix, prefix length instead of address, mask.
Question 2
Which one of these statements is true of OSPF type 5 LSAs?
A. They are used to summarize area routes to other areas.
B. They are used in not-so-stubby areas to propagate external routes.
C. They are used to notify areas of the ASBR.
D. They are flooded to all areas (external route).
Answer: D
Explanation
Type 5 external link LSAs are used to advertise external routes originated from an ASBR. They are flooded through the whole OSPF domain.
(Note: The dashed arrows show the directions of LSAs in this example)
Below is a summary of OSPF Link-state advertisements (LSAs)
Router link LSA (Type 1) – Each router generates a Type 1 LSA that lists its neighbors and the cost to each. LSA Type 1 is only flooded inside the router’s area, does not cross ABR.
Network link LSA (Type 2) – is sent out by the designated router (DR) and lists all the routers on the segment it is adjacent to. Types 2 are flooded within its area only; does not cross ABR. Type 1 & type 2 are the basis of SPF path selection.
Summary link LSA (Type 3) – ABRs generate this LSA to send between areas (so type 3 is called inter-area link). It lists the networks inside other areas but still belonging to the autonomous system and aggregates routes. Summary links are injected by the ABR from the backbone into other areas and from other areas into the backbone.
Summary LSA (Type 4) – Generated by the ABR to describe routes to ASBRs. In the above example, the only ASBR belongs to area 0 so the two ABRs send LSA Type 4 to area 1 & area 2 (not vice versa). This is an indication of the existence of the ASBR in area 0. Note: Type 4 LSAs contain the router ID of the ASBR.
External Link LSA (LSA 5) – Generated by ASBR to describe routes redistributed into the area (which means networks from other autonomous systems). These routes appear as E1 or E2 in the routing table. E2 (default) uses a static cost throughout the OSPF domain as it only takes the cost into account that is reported at redistribution. E1 uses a cumulative cost of the cost reported into the OSPF domain at redistribution plus the local cost to the ASBR. Type 5 LSAs flood throughout the entire autonomous system but notice that Stubby Area and Totally Stubby Area do not accept Type 5.
Multicast LSA (Type 6) are specialized LSAs that are used in multicast OSPF applications.
NSSA External LSA (Type 7) – Generated by an ASBR inside a NSSA to describe routes redistributed into the NSSA. LSA 7 is translated into LSA 5 as it leaves the NSSA. These routes appear as N1 or N2 in the ip routing table inside the NSSA. Much like LSA 5, N2 is a static cost while N1 is a cumulative cost that includes the cost upto the ASBR
(Reference: http://www.cisco.com/en/US/tech/tk365/technologies_white_paper09186a0080094e9e.shtml#appa1)
Question 3
Which OSPF LSA type does an ASBR use to originate a default route into an area?
A. LSA 1
B. LSA 3
C. LSA 4
D. LSA 5
E. LSA 7
Answer: D
Explanation
By default, the OSPF router does not generate a default route into the OSPF domain. In order for OSPF to generate a default route, you must use the default-information originate command. With this command, the router will advertise type 5 LSA with a link ID of 0.0.0.0.
(Reference: http://www.cisco.com/en/US/tech/tk365/technologies_configuration_example09186a00801ec9f0.shtml)
Question 4
Refer to the exhibit. Routers A and B are directly connected and running OSPF, but they are unable to form a neighbor relationship. What is the most likely cause?
|
Router A relevant configuration: router ospf 1 Router B relevant configuration: router ospf 10 |
A. The routers are not on the same network.
B. The network statements do not match.
C. The process number does not match.
D. The MTU does not match.
E. The OSPF cost does not match.
F. There is a physical issue with the cable.
Answer: D
Explanation
OSPF sends the interface MTU in a database description packet. If there is a MTU mis-match, OSPF will not form an adjacency and they are stuck in exstart/exchange state. The interface MTU option was added in RFC 2178. Previously, there was no mechanism to detect the interface MTU mismatch. This option was added in Cisco IOS Software Release 12.0.3 and later.
If the router with the higher MTU sends a packet larger that the MTU set on the neighboring router, the neighboring router ignores the packet and the neighbor state remains in exstart.
Note: By default, the MTU for Ethernet is 1500 bytes. We can check the OSPF adjacency process with the command “show ip ospf neighbor”.
(Reference: http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080093f0d.shtml)
Question 5
Which two of these steps are minimum requirements to configure OSPFv3 under IPv6? (Choose two)
A. Configure a routing process using the command ipv6 router ospf [process-id].
B. Add the network statement for the interfaces on which OSPF will run.
C. Configure OSPF on the interface that it will run on.
D. Use the passive-interface command on the interfaces on which OSPF should not run.
E. Enable routing.
Answer: C E
Explanation
The first step to configure OSPFv3 under IPv6 is to enable IPv6 unicast routing:
R1(config)# ipv6 unicast-routing
Also we need to enable the OSPF process:
R1(config)# ipv6 router ospf 1
There are a few changes in configuring OSPFv3 vs OSPF for IPv4. Instead of using the “network” and “area” commands in ospf router configuration mode you now configure OSPFv3 on a per interface basis using the ipv6 ospf
R1(config)# interface fa0/0
R1(config-if)# ipv6 ospf 1 area 0
Note: The “network” command does not exist in OSPFv3.
Question 6
Refer to the exhibit. How would you get the 1.1.1.1 network into the OSPF database?
A. Configure RTA as an ASBR.
B. Redistribute connected routes on RTA into OSPF.
C. Set up a virtual link between area 1 and area 0.
D. Set up a virtual link between area 1 and area 2.
E. Add a static route into RTB and enter it into OSPF.
F. Place a network 1.1.1.0 0.0.0.0 command into RTB.
G. Set up a unique router ID on RTA using an RFC 1918 address.
H. Change area 0 on RTB to area 1
Answer: C
Explanation
Recall that in OSPF, area 0 is called backbone area and all other areas connect directly to it. In the exhibit above, area 1 is not directly connected with area 0 so we need to set up a virtual link between area 1 & area 0 so that the networks in area 1 can be recognized in area 0. The virtual-link configuration is shown below:
RTB(config)#router ospf 1
RTB(config-router)#area 2 virtual-link 1.1.1.1
RTA(config)#router ospf 1
RTA(config-router)#area 2 virtual-link 2.2.2.2
Notice that the router-id in the “area … virtual-link
Question 7
The core of a network has four routers connected in a square design with Gigabit Ethernet links using /30 subnets. The network is used to carry voice traffic and other applications. Convergence time is taking more than expected. Which three actions would you take to improve OSPF convergence time? (Choose three)
A. Increase MTU of the interfaces to accommodate larger OSPF packets.
B. Change the network type to point-to-point on those links.
C. Reduce SPF initial timer.
D. Increase hello interval to avoid adjacency flapping.
E. Enable OSPF.
Answer: B C E
I WANT TO APPEAR IN ROUTING & SWITCHING WRITTEN EXAM. CAN ANY BODY EMAIL ME THE CURRENT ROUTING & SWITICHING WRITTEN QUESTIONS. THANKS
I think Question 2’s correct answer should be closer to D. They are flooded to all areas except sub areas (external route). for it to be correct.
Q5, Does not the answers A, C and E be correct? Why A is not correct or is not one of the best answers?
q5
I think this question is taken based on this document
http://www.cisco.com/en/US/docs/ios/ipv6/configuration/guide/ip6-ospf.html#wp1070061
You will see under the section how to implement ospf for ipv6 it only has 1 REQUIRED thing configure interface and in the comments it says that OSPF IPV6 routing is disabled by default.
who can please tell me that why the answers can improve ospf convergence time about Q7?
Q5.
Cisco usually trap us for ipv6, I also found NAT-PT problem in Cisco document…
But for exam, we have to following the game
Sorry for the typo
Which two of these steps are minimum requirements to configure OSPFv3 under IPv6? (Choose two)
C. Configure OSPF on the interface that it will run on.
E. Enable routing.
Answer: C E
I have just tested this on GNS3 and the options C and E are correct, but we are assuming that their is a 32 bit IPV4 address configured on the router for OSPFv3 to select as a RID other the process will not start, otherwise the neighbors do form with the OSPF process set under the interfaces Another Cisco question that is right but wrong
I am confused by Question 7. The question states that we need to ” improve OSPF convergence time “. In my opinion, this rules out answer E (“enable OSPF”). In order to improve OSPF, OSPF needs already to be enabled. Instead, i believe answer A is correct. Increasing the MTU size on a Gigabit interface does not harm voice, and can improve OSPF convergence time.
henk, I do agree with you A,B,C should be the correct answer
Question 4 is definately A, one of the OSPF requirements is that the neighbors are on the same primary subnet.
Forget i said that, i thought it was a /30 🙂
Question 7)
I am a little confused about OSPF throttling, or reducing the SPF initial timer. This helped me though:
The OSPF SPF Throttling is configured using the command timers throttle spf OSPF router configuration command.
spf-start: Initial delay to schedule an SPF calculation after a topology change. Range is 1 to 600000 milliseconds.
spf-hold: Minimum hold-time between two SPF calculations. Range is 1 to 600000 milliseconds.
spf-max-wait: Maximum wait between two SPF calculations. Range is 1 to 600000 milliseconds.
This command is used to delay the SPF algorithm being executed during network instability. SPF Is very CPU intensive 🙂
@Sarah what do u say about?
Area Border Router (ABR) is a router located on the border of one or more OSPF areas that
connect those areas to the backbone network. An ABR will inject a default route into which two types of areas? (Choose two.)
A. Area 0
B. NSSA
C. Totally stubby
D. Stub
Answer: C,D
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thanks
Q4: So nobody noticed the router ospf number doesnt match on the two routers? Shouldn’t the answer be C?
disregard my comment. I am obviously sleepy.
Sarah, about your afirmation: Question 4 is definately A, one of the OSPF requirements is that the neighbors are on the same primary subnet.
They are in the same subnet /22 and eache router is advertise just a network /24, so the answer D is the correct because the default MTU was changed on Router B
Question 2: Answer D is correct but I think that answer C also, because on explanation have: External Link LSA (LSA 5) – Generated by ASBR to describe routes redistributed into the area….
So answer C (They are used to notify areas of the ASBR.) is correct.
@Expe0626
This is true, the only type of network where a default route is not injected into is an NSSA
Regards,
Sarah
Question 5)
I testing this in GNS 3 using a simple Point to point connection (R3 ————R4)
R3(config)#int fa1/0
R3(config-if)#ipv6 ospf 1 area 0
R3(config-if)#end
R3#s
00:03:47: %OSPFv3-4-NORTRID: OSPFv3 process 1 could not pick a router-id,
please configure manually
R3#show run int fa1/0
00:03:48: %SYS-5-CONFIG_I: Configured from console by console
R3#show run int fa1/0
Building configuration…
Current configuration : 132 bytes
!
interface FastEthernet1/0
no ip address
duplex auto
speed auto
ipv6 address 2000::1/64
ipv6 enable
no clns route-cache
end
R3#show ipv6 ospf
%OSPFv3: Router process 1 is not running, please configure a router-id
R3#
The command i entered was taken out of the interface becuase OSPF wasnt configured globally.
R3(config)#ipv6 router ospf 1
R3(config-rtr)#router
R3(config-rtr)#router-id 1.1.1.1
R3(config-rtr)#int fa1/0
R3(config-if)#ipv6 ospf 1 area 0
R3(config-if)#exit
R3(config)#exit
R3#show run int
00:04:43: %SYS-5-CONFIG_I: Configured from console by console
R3#show run int fa1/0
Building configuration…
Current configuration : 152 bytes
!
interface FastEthernet1/0
no ip address
duplex auto
speed auto
ipv6 address 2000::1/64
ipv6 enable
ipv6 ospf 1 area 0
no clns route-cache
end
R3#
The command now stays in there and show ipv6 ospf works:
R3#show ipv6 ospf
Routing Process “ospfv3 1” with ID 1.1.1.1
SPF schedule delay 5 secs, Hold time between two SPFs 10 secs
Minimum LSA interval 5 secs. Minimum LSA arrival 1 secs
LSA group pacing timer 240 secs
Interface flood pacing timer 33 msecs
Retransmission pacing timer 66 msecs
Number of external LSA 0. Checksum Sum 0x000000
Number of areas in this router is 1. 1 normal 0 stub 0 nssa
Area BACKBONE(0) (Inactive)
Number of interfaces in this area is 1
SPF algorithm executed 1 times
Number of LSA 3. Checksum Sum 0x021F3B
Number of DCbitless LSA 0
Number of indication LSA 0
Number of DoNotAge LSA 0
Flood list length 0
R3#
Something else worth mentioning, if i take the ipv6 ospf 1 area 0 command out of the interface and have no interfaces in the OSPF process, i still have a running OSPF process:
R3(config)#int fa1/0
R3(config-if)#no ipv6 ospf 1 area 0
R3(config-if)#end
R3#show run int fa1
00:05:32: %SYS-5-CONFIG_I: Configured from console by console
R3#show run int fa1/0
Building configuration…
Current configuration : 132 bytes
!
interface FastEthernet1/0
no ip address
duplex auto
speed auto
ipv6 address 2000::1/64
ipv6 enable
no clns route-cache
end
R3#
R3#
R3#show ipv6 ospf
Routing Process “ospfv3 1” with ID 1.1.1.1
SPF schedule delay 5 secs, Hold time between two SPFs 10 secs
Minimum LSA interval 5 secs. Minimum LSA arrival 1 secs
LSA group pacing timer 240 secs
Interface flood pacing timer 33 msecs
Retransmission pacing timer 66 msecs
Number of external LSA 0. Checksum Sum 0x000000
Number of areas in this router is 0. 0 normal 0 stub 0 nssa
R3#
I had no idea how to approach this bfeore-now I’m locked and loaded.
Sarah, for Q5, the ‘ipv6 router ospf 1’ would have been automatically generated when OSPFv3 was enabled on the first interface if you had the Router ID present at the time. You could have had the Router ID just by giving an IPv4 address to a loopback. But you created the Router ID by going into the ‘ipv6 router ospf 1’ mode.
The question asked for minimum requirements. ‘ipv6 router ospf 1’ could be automatically generated if other steps were taken first. So it is optional. So A is not correct.
The correct answer is C, E
thanks pakdude.
Q7 answer from rstut is valid. there’s this question in my head when i see this q in my exam today “it is already ospf, why would bother enabling it? and what’s wrong with MTU?”. as henk said, MTU does not harm voice, but OSPF convergence do not considering MTU. then i imagining doing this ospf changes, and before i will change anything in a segmen, i would disable ospf in the segmen first (by erasing authentication for example), then do some changes and after finish, i reenable ospf by pasting the previous authentication line and OSPF adjacency will reconverge. so i choose E today and got 1000. thanks rstut.
quote “but OSPF convergence do not considering MTU” what i mean here changing MTU does not make OSPF convergence faster.
Q2) Type 5 (AS External LSA’s) are flooded to all areas.
Q3) Default route can be advertise in Type 3 LSA (Network Summary LSA which is why you can see a default route on a router in Totally Stubby area) or Type 5…but for type 5 a router should be ASBR and it can only be ASBR if it “redistributes” or advertise a default route by “Default-information originate” command. OSPF do not advertise Default route in it’s domain like RIP does.
Q4) MTU mismatch will make the routers stuck in “Exstart state” so no adjacency.
Q6) ABR is not just a border router but for a router to satisfy to be an ABR it should have an interface in Area 0 (Backbone area). The reason being inter area route information is sent by Backbone and ABR send it’s summarized topological information of it’s attached area’s into backbone which will propagate the summary into other area’s. So every ABR should be attached to Backbone area and if it’s not it can be with the help of “Virtual-link” (On Cisco routers it can be seen as fully adjacent point-to-point link).
Q7) First of all i can’t see any where in the question that OSPF is running before hand so cut assuming any thing (One of the reason people fail in CCIE). Enable OSPF is correct choice here. Second “reducing SPF initial” timer will make convergence better, it means in simple terms that do not generate LSA until default of 5 milliseconds after link failure…so reducing it to “1” can be good don’t you think??? Plus the timers in this command are (timers throttle spf [initial wait timer ] [Increment timer] [Max_Wait timer]…like i said initial timer specifies the time after an LSA is generated, next it sets the timer to [initial timer + increment timer] = time for which next LSA is scheduled, and the timer will never incremented above MAX-Wait timer 🙂 Hope this helped…Haven’t started studying IPv6 so can’t comment on that 🙂
and third option for Q7 is point-to-point because links with /30 prefix will automatically an interface selected as DR and other as BDR (DR, BDR is function of interface not Router). So if you configure network type on each interfaces as point-to-point there will be no DR, BDR election and it can save some CPU cycles.
Sorry guys i wrote LSA instead of SPF (The mechanism is same for both timers but the command is different). For LSA exponential backoff (Timers throttle lsa all [initial increment max]) and for SPF calculations (Timers throttle spf [initial increment max]), Plus there are two more commands to remember when dealing with SPF calculation (i.e. timers spf spf-delay and timers spf spf-holdtime)…SPF recalculation for Route(s) will not start once SPF timer is expired (timers spf spf-delay) and the total delay between consecutive calculation can be influenced by (timers spf spf-holdtime).
HTH
Rizwan
Q7 must be BCE or ABC – please someone confirm one way or another –
Enable OSPF is just so wrong to have there to begin with. I am almost guessing that its a typo – like they INTENDED to put “Enable OSPF summarization” — or something like that and it got cut off because for this exam to be asking you to improve something by enabling it is just crazy.
Someone said that you would make changes then disable/enable after the changes and I disagree. This is either outright wrong or its a mistake.
Someone please prove definitely?
Hello every CISCO guys
Im preparing to get CCIE written exam and I would appreciate someone who tell me is there any lab or simlet question like there is in CCNA and CCNP in CCIE or not?
Thank you so much
Khan ,
In Q4, answer C is not correct because neighboring routers’ router ospf process-id commands do not have to be configures with the same process-id parameter to become neighbors
QUESTION 41
Refer to the exhibit.
Router RTB is performing one-way redistribution from RIP to OSPF. Which outgoing interface will router RTD choose for packets to the 192.168.0.0/24 network, and why?
A. Fa0/1, because OSPF is a link-state routing protocol
B. Fa0/0, because RIP is a distance vector protocol
C. Fa0/0, because RIP has a higher administrative distance
D. Fa0/0, because OSPF has a lower administrative distance
E. Fa0/1, because OSPF has a lower administrative distance
F. Fa0/1, because RIP has a lower administrative distance
Answer: E
Section: Misc
—————————————————————————————————————-
QUESTION 93
Refer to the exhibit.
Router RTB is performing one-way redistribution from RIP to OSPF. Which outgoing interface will router RTD choose for packets to the 192.168.0.0/24 network, and why?
A. Fa0/1, because OSPF is a link-state routing protocol
B. Fa0/0, because RIP is a distance vector protocol
C. Fa0/0, because RIP has a higher administrative distance
D. Fa0/0, because OSPF has a lower administrative distance
E. Fa0/1, because OSPF has a lower administrative distance
F. Fa0/1, because RIP has a lower administrative distance
Answer: D
Section: OSPF
Explanation/Reference:
Explanation:
Hello every CISCO guys
I really do not understand the answer to this problem. Please answer what to teach.
Thank you so much
I have check that question in dumps i think there is a route redistribution in the other ASBR (RTB) RIP int OSPF … so RTD has information in both topologies RIP and OSPF, and it has to elect which one is better, and the tie-breaker is AD (adminitrative Distance)
Rip pointing to the RIP domain (left i dont remember the interfaces please post the picture)
OSPF pointing to the OSPF domain (to the right)
RIP –> AD = 120
OSPF –> AD = 110
Lower is Better in AD so the correct answer depends on the exibit but i remeber that’s the one to the right (to the OSPF domain and the longer path)
Hope this helps
Regards
I’d like to know about this question
http://i46.tinypic.com/2cfrrwx.jpg
I’m agree with the answer but i would have thought that the real answer is just 10.1.5.0/24 network because the question says just Type 2 in the database.
I already simulated in GNS3 and this is the output:
R4#sh ip ospf database
OSPF Router with ID (10.1.1.0) (Process ID 1)
Router Link States (Area 0)
Link ID ADV Router Age Seq# Checksum Link count
10.1.1.0 10.1.1.0 28 0x80000002 0x001C47 2
10.1.5.1 10.1.5.1 5 0x80000003 0x007AA4 3
10.1.5.2 10.1.5.2 6 0x80000002 0x00924D 1
10.1.5.3 10.1.5.3 6 0x80000002 0x00904C 1
Net Link States (Area 0)
Link ID ADV Router Age Seq# Checksum
10.1.5.3 10.1.5.3 6 0x80000001 0x00AF2A
R4#
R4#
R4#sh ip ospf database network
OSPF Router with ID (10.1.1.0) (Process ID 1)
Net Link States (Area 0)
Routing Bit Set on this LSA
LS age: 35
Options: (No TOS-capability, DC)
LS Type: Network Links
Link State ID: 10.1.5.3 (address of Designated Router)
Advertising Router: 10.1.5.3
LS Seq Number: 80000001
Checksum: 0xAF2A
Length: 36
Network Mask: /24
Attached Router: 10.1.5.3
Attached Router: 10.1.5.1
Attached Router: 10.1.5.2
R4#
Regards
@Gonzalo
The infomration in the question is not enough to answer the question, however, in my opinion the best solution is D (R3 will not generate a Network LSA in this network!!).
Type 2 LSAs are generated by DR. There is one DR in every broadcast segment.
For segment 10.1.5.0/24, it looks as if 10.1.5.3(highest IP – still may or may not be its Router ID) will be the DR (This is the missing nformation i am referring to – We dont know for sure who the DR will be as there is no information about Router ID).
By the looks of it R1 is the DR for 10.1.5.0/24 segment & hence R1 will generate Type 2 LSA for the segment.
As far as 10.1.1.0/31 is concerned, a /31 address is mostly configured on Point to Point Segment (I say MOSTLY because it still can work on broadcast interface as well). There is no DR / BDR eclection on Point to Point interface & hence no question of Type 2 LSA. (Again the missing information is what network type are we using between R3 & R4 & If is is broadcast what is the Router ID).
So by the looks of it R3 would not generate a Type 2 LSA .
Thanks Naren for your answer. In my topology R1 won the DR election so the Type 2 LSA was NOT generated by R3 but of course if i shut R1 and R2 things would be different because of no preemption in DR election.
Best Regards
Please, can you PM me and tell me few more things about this, my homie am really fan of your site! my homie just subscribed to your feed.
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Q4 is definitely A. How can a router communicate or form adjacency in first place when they don’t belong to the same network segment?
Sorry, above comment is incorrect. They belong to /22. So they are fine. Answer is D. MTU on one side is 512 & another side left to default (i.e 1500).
Q7 is wrong, OSPF is already enabled. Changing MTU won’t disable it, it will however clear your neighbourships.
The bloke who reckons he got 1000 is talking parp.
this site is for fake CCNA , CCNP
Inertviewed a CCNP who doesnt know how to connect a router and a PC……….SHAME
@truth. haha. Well, there are phds in CS cannot write code. At least he got a chance for an interview.
Question 7 should be BCD, this question is about IPv4, /30 and p2p together usually points to IPv4 so there is no reason to enable OSPF, OSPF is already enabled. Besides it’s asking to improve OSPF convergence which means OSPF was already running.
Q2 is an annoying question as we know that type 5 LSA’s are not accepted by stub and totally stub areas. However this is a trick question as LSA’s ARE flooded throughout the entire OSPF domain but a stub router will not accept it. Therefore D is correct even though it doesn’t sound/feel correct!
Exam F, Q19
which of these statements about OSPF external LSA (type 5) is correct?
1,2,3 options are definitely incorrect
4. OSPF external LSA’s are automatically flooded into all OSPF areas, unlike type 7 LSAs, which require redistribution to be configured
5. External network LSAs (type 5) redistributed from other routing protocols into OSPF are not permitted to flood into a stub area
I would have said definitely number 5, but latest VCE file says 4! I think 4 is incorrect. Any thoughts?
Why we need router-id in ospf proccess