RIP advertisements coming only from Secondary HSRP

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Sep 30th, 2010
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I have a setup of 3 routers with 2 configured for HSRP and third is just collecting RIP advertisments from earlier two. What I see is third router gets RIP advertisements only from Secondary HSRP router and not from the primary. My RIP config is pretty simple with RIP v2 and network statements. Does anyone know how should I troubleshoot this? I cannot run debug on these routers as they are in live network.


How does the third router decide which advertisment to prefer , if it gets advertisments from both?


Thank you.


Shivani

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Peter Paluch Thu, 09/30/2010 - 13:05
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Shivani,


Is it possible that the first router has nothing to advertise in RIP, and so - because of the split-horizon rule - does not send any RIP updates? That would be my first idea. Without seeing the topology of your network, I cannot say more. In general, HSRP should not have any effect on RIP updates.


How does the third router decide which advertisment to prefer , if it gets advertisments from both?


Simply by taking the shortest path - just as it would with any internal routing protocol even without HSRP. If both routers advertise the same shortest path then the third router will use them both for load balancing. Once again, the HSRP is for end stations, not for routers (nor should it be ever deployed for routers - routers have routing protocols and don't need HSRP). The activity of HSRP cannot have any effect on the logic in RIP or any other routing protocol.


Best regards,

Peter

shivani.sharma Thu, 09/30/2010 - 20:45
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Hello Peter,


Thanks for your response. I do understand now what you explained about HSRP not being related to routing protocol.


Attached is a draft of the network setup. I have used example IP subnets. In this scenario, R3 gets RIP routes only from R2 and not from R1.


In my live setup I do have long list of RIP routes in R1. But they do not get advertised to R3. Same routes are in R2, which do get advertised to R3.

Attachment: 
shivani.sharma Wed, 10/06/2010 - 11:38
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Hello Shivlu


Attached is the output for sh ip route for each router. Please note that I have changed some public ips, which you will now see as 172.x.x.x. R1 has rip and ospf routes from other sources and I have configured R1 to re-distribute these routes(rip and ospf) to R3. But R3 do not get any RIP updates from R1. Please also note the attached updated diagram according to the output. Also, R3 has huge ip route table, so I just attached the output for "show ip route | i 10.144.2.7" , in order to show any routes from 10.144.2.71 and 10.144.2.72.

Thank you.


Shivani

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