Refer to the exhibit. A network engineer is in the process of implementing IS -IS Area 1 and Area 2 on this network to segregate traffic between different segments of the network. The hosts in the two new areas must maintain the ability to communicate with one another in both directions. Which additional change must be applied?
To ensure communication between hosts in the two areas, at least one router in each area needs to be configured to connect Level 1 (L1) and Level 2 (L2) routing. Reconfiguring routers R2 and R5 as L1/L2 routers will create sufficient adjacency between the two areas. R2 will have L1 adjacency with R1 and L3, and L2 adjacency with R4. Similarly, R5 will have L1 adjacency with R3 and L2 adjacency with R4 and R6. This configuration ensures the necessary connectivity between the two areas without redundancy.
I think A because having R2 as level 1/2 will make the necessary adjacency to R4 which is an L2 and in Area 2. You need L2 peer to connect different areas not L1. B I'm not sure it is wrong but it seems redundant to make R1 and R6 Level 1/2 C is wrong because it doesn't make any router in Area 1 (which has L1 only routers) border to Area 2 an L2 router D is wrong because of the OR as mentioned by others.
Agree for all of the same reasons.
incorrect. please take notice of answer D saying "R3 OR R4". we need to maintain end-to-end connectivity in both directions. if you configure R3 for example as Level 1/2 and leave off R4 as level 2.. you broke a rule... R2 cannot form direct connectivity with R4 as L1 --> L2 neighborships are not allowed. i vote for answer A
C can't be correct as again direct connectivity between L2 and L1 is not allowed. B might seem right but it is a horrible solution - it eliminates the scalability and flexibility of IS-IS. D is incorrect and explained in my answer above. A is the correct answer
R2 ==> L1/L2 ==> Has L1 with R3 and L2 with R4 and L1 with R1 R5 ==> L1/L2 ==> Has L1 with R3 and L2 with R4 and L2 with R6
D is excluded: In case we configure R3 as L1/L2, R3 and R5 will have a L2 adjacency (L2 works between different areas), and R3 will become an ABR for area 1 In case we configure R4 as L1/L2, R4 and R2 will not establish any adjacency (R2 is L1, and L1 doesn't work between different areas) A does the job (partially): R2 and R4 will establish a L2 adjacency (L2 works between different areas), and R2 will become an ABR for area 1 R3 and R5 will not establish any adjacency (R3 is L1, and L1 doesn't work between different areas)
A is correct
Any answer is correct which upholds the contiguous nature of the level 2 backbone while providing an exit point to Level 1 routers However some answers are less optimal than others D: Reconfigure only one of R3 or R4 to L1/L2, This answer fulfils the objective but leaves the other router with an unused link since it cannot communicate with one of its neighbors. traffic must take a circuitous path to the far end R1 router. It would be better to convert both to L1/L2 B: Reconfigure routers R1, R2 R5. and R6 as Level 1/Level 2 routers. This solution does little to segregate the routing table because now have two massive routing tables (L1 and L2) which span across the network from R1 to R6 A: Reconfigure routers R2 and R5 as Level 1/Level 2 routers This effectively separates the L1 and L2 areas into 4 routers each and allows all links to be used C: goes against the original aim I would go with answer A:
I will have to go with option A... I read the following: "By default, the L1/L2 router allows one way passage of prefixes from L1 Area to L2 Area, but not in reverse." https://www.cisco.com/c/en/us/support/docs/ip/integrated-intermediate-system-to-intermediate-system-is-is/200293-IS-IS-Adjacency-and-Area-Types.html There is more within the link... I g2g, check it out.
Tried each configuration in a lab (used loopbacks on R1 and R6 as the two hosts that need to communicate): A: R1 - gets a default route as it is a L1 router. R6 gets the prefix as it is an L2 router. B: R1 and R6 both have the corresponding prefix (i.e. no default route). Communication between the two loopbacks work. C: --- did not do this as it is obviously wrong -- D: Configured R3 as a L1/L2 router. R1 retrieved a default router from R3. R6 actually has the 1.1.1.1/32 route in its routing table. R1 and R6 are able to communicate with one another. Seems like the routing table of R1 and R6 are the same whether you do configuration A or D... however, routing path is different (in D it goes only through R3, while in A it load balances). B is the only configuration that offers a routing table that is both routes in the routing table. Honestly... not sure what the correct answer would be, I would still go with A... idk.
I initially picked A, but I think Cisco's answer will be D. A and B are basically the same thing. Changing R2 to L1/L2 is the only change that enables end-to-end connectivity. All other changes in A and B (including R5) do nothing. If R5 is changed to L1/L2, it will still not have a neighborship with R3. That's why I'm saying since answers A and B are basically the same answer, I think neither of them are what Cisco considers the right answer. If I get this question, I'll choose D, but I agree with everyone saying D is wrong.
it say's R3 0r R4 not R3 "and" R4. B is not similar to A. NO need for router 6 to be l1/l2 .. it should be core/backbone and it is not stretching L2 to L1. Only answer that makes sense is A R2 ==> L1/L2 ==> Has L1 with R3 and L2 with R4 and L1 with R1 R5 ==> L1/L2 ==> Has L1 with R3 and L2 with R4 and L2 with R6
Hmm, A,B,D answers can be used to maintain end-to-end connectivity, but if we're going to take into consideration on the ease of configuration, choice D will be the best one because you will only need to configure R3 as L1/L2 to do it. That is, if we treat the OR statement as the exam trying to confuse us. After all, it said either R3 or R4, means we just only need to use one, not both. And the correct one lies on R3.
In any case, I hope this one doesn't appear in my exam lol.
Agree with D ,
I'd say answer is B although only required for R2 and R5. D would be ok for R3 but not R4 as it would still have no L1 adjacency with R2 due to area mismatch.
Reading it again, Answer A would be better instead of B.
D is the Correct answer