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I wanted to understand how redundancy works when we implement Frame Relay to connect between different office locations. Consider the topology here I have two sites A and B each has a pair of Routers (R1, R2), (R3, R4) each belonging to each site.

R1, R2 pair is connected to R3, R4 pair over Frame relay such that R1 can connect to R3 (via dlci 103) and R4 (via dlci 104) similarly R2 can connect to R3 (via dlci 203) and R4 (via dlci 204) and vice versa using point to point links, all the routers R1 through R4 belongs to same subnet.

For the internal network of R1, R2 pair they are running HSRP for redundacy similarly R3 and R4 as well.

My question is in such a scenario where R1 or R2 fails how does R3 or R4 route the traffic which is meant for R1/R2 network (I understand we can use Routing protocols such as EIGRP to detect if R1/R2 are down). Is there any other parameters we consider apart from routing protocols?

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  • Did any answer help you? if so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you could provide and accept your own answer. – Ron Maupin Aug 12 '17 at 4:04
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A router failure is a clean down/down scenario whereby routing protocols will handle updating of reachability and HSRP will take care of routing for the local subnet(s) as well as provide the WAN connectivity to the remote site.

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  • Thanks for your answer, can you elaborate with an example how redundancy works not for internal network but for external network (public access) – charan Jul 30 '15 at 22:17
  • The remote router terminating the DLCI, which remains up, will miss keepalive(s) and ultimately know that his peer is dead. – Ronnie Royston Jul 30 '15 at 22:22

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