Refer to the exhibit. An engineer configured R2 and R5 as route reflectors and noticed that not all routes are sent to R1 to advertise to the eBGP peers.
Which iBGP routers must be configured as route reflectors to advertise all routes to restore reachability across all networks?
To restore reachability across all networks, the iBGP routers R4 and R5 must be configured as route reflectors. In this network, R1 is an edge router and using it as a route reflector is not recommended. Configuring R4 as a route reflector with its clients, which include R1, R5, and R8, will ensure that all loopback addresses are advertised correctly. Additionally, R5 should be a route reflector with R2 as its client to ensure that routes from R2 are properly advertised. This setup avoids potential issues with route reflection and ensures full reachability within the AS. Therefore, configuring R4 and R5 as route reflectors is the correct approach.
C - confirmed in the lab. All that is needed is R4 to be a RR with R1 as its client and that gets all loopbacks in routers BGP tables. So having R2, R5 and R4 also works. R4 and R5 is the only option that works without any other RR configuration. So the answers assume we roll back the engineers config and take a fresh start. Definitely C.
Tested further, only R4 is needed as RR as a minimum. With what Alimo123 says below, its bad practice to have an edge router as RR so that would eliminate answer A, still C as the answer, but R5 is not needed as RR.
Apart from the test, what is the reason? RR rules do not help here apart from the fact the two RRs must be in a mesh, that means connected (so it cannot be R1 and R5). If we exclude answers B and D we have solutions A and C that means R4 and R1 or R5. We could exclude R1 because it is better not to use an edge router as RR but I have not found any real reason to choose C in accordance with RR rules. Explanation found here: https://itexamanswers.net/ccnp-enarsi-300-410-dumps-full-questions-with-vce-pdf.html/2 seems to be wrong because RR have to speak to each other. So far, I cannot really say answer is C
I also confirmed solution "C" in the lab (CML). RR = R4 (it's clients = R1, R5, R8) and RR = R5 (it's client R2). R2's loopback has not been advertised to R4 and R8 (and vica versa) until R2 became the client of RR R5. In my lab, full reachability was achieved with R4 and R5 being RRs. (Maybe I am missing something as others stated that R4 would be enough as RR.)
I really dont understand why R2 and R5 as RR don't work.
That would work also. But probably not the answer they are looking for.
Another fine example of Cisco getting you to choose the best option. Off the bat, you can eliminate A & B, since RR on an edge router (R1) is not recommended. We already know, from the question that D won't work. C is the best answer from the options provided.
It is not a good practice to have an edge router as RR
There is no difference between the setup of R2 & R5 and R4 & R5. So the same problem would exist with C. R1 R4 (A) would be better but it would still be a poor design. Based on the diagram the best answer would be R2 & R4.
Just R4 as RR with R1, R5, and R8 as clients would work, but is not an option. Options C and D both work, but C seems more likely to be what they want.
Hi timtgh, R1 is not necessary as client since it is already connected to the rest of the network.
A poorly worded and considered example. but i would settle for C. R4 has to be a RR
It more sense configure reflectors on R1 and R5
No it does not. Because R1 and R5 cannot exchange routes since they are iBGP neighbors.
JOKERR is right: It is important to note that route reflectors must form a full mesh connectivity among themselves and each client peer with only its route reflector. Full mesh among route reflectors is not apparent until there are at least three route reflectors (see Figure 9.12(d)). Source: https://www.sciencedirect.com/topics/computer-science/route-reflector
The client does not know that he is a client, he simply sends routes towards the neighbor.
C is correct
C works for R4, but not R5. Route reflects have to have a route to the destination to reflect it. They will only have a route when they are connected to the ebgp router (R2 & R4). After this the route will show *i in the show ibgp table and not forward. Poor design but the answer is A. C wouldn't be any different than the current setup that is more than one hop away.
I think the answer is C too. If R5 and R2 have the same cluster-id, then R8 loopback coming from R5 will never be advertised to R1 because it will be discarded by R2. The real interesting question here is WHY do we have a question like this ? Multiple route reflectors topic is excluded in the exam topics.. And why don't they say that the cluster-id is the same ? Poor cisco question as always. Makes me want to dump more.
Hello, I made some tests with GNS3 and it seems A,C and D are good solutions since all loopback interfaces are reachable. But answer D is excluded by the exercise and R1 is better not to use as RR. So the only answer remaining is C. Studybuddy is correct when he says only R4 is enough but if you make R1 as client, R2 is not reachable. The right thing to do is set R4 as RR and set R5 and R8 as RR client. I hope it may help.
R2: interface FastEthernet0/0 ip address 192.168.2.2 255.255.255.0 duplex half ! interface FastEthernet1/0 ip address 192.168.5.2 255.255.255.0 duplex half ! router bgp 400 bgp log-neighbor-changes network 192.168.2.0 network 192.168.5.0 neighbor 192.168.2.1 remote-as 400 neighbor 192.168.5.5 remote-as 400 neighbor 192.168.5.5 route-reflector-client R4: interface FastEthernet0/0 ip address 192.168.1.4 255.255.255.0 duplex half ! interface FastEthernet1/0 ip address 192.168.4.4 255.255.255.0 duplex half ! interface FastEthernet2/0 ip address 192.168.10.4 255.255.255.0 duplex half ! router bgp 400 bgp log-neighbor-changes network 192.168.1.0 network 192.168.4.0 network 192.168.10.0 neighbor 192.168.1.1 remote-as 400 neighbor 192.168.4.8 remote-as 400 neighbor 192.168.4.8 route-reflector-client neighbor 192.168.10.5 remote-as 400 R2 &R4 are working perfectly fine
Why can't RR2 send routes received from RR5 to R1?
Why not R2 and R4?
I did lab and R2 and R4 work perfectly fine
Then I would replace in the question "routers must be" with "routers can be" or somehow change it.