S7700 RPF failure caused C-BSR message ignored

Publication Date:  2015-12-31 Views:  280 Downloads:  0
Issue Description

Product:

campus switch S7700


Problem:

PIM SM C-BSR message ignored due to RPF Failure when using VRRP virtual IP as next-hop address




Alarm Information

XXX xx 2015 14:49:43.670.1 S7700 PIM/7/RP:(public net): Receive BSR packet. And use BSR Mechanism now. (S034326)

XXX xx 2015 14:49:43.670.2 S7700 PIM/7/RP:(public net): RPF Failure. 192.168.1.2 not next hop to C-BSR <IP address>, ignored. (S18651)

XXX xx 2015 14:49:43.670.3 S7700 PIM/7/RP:(public net): Rejecting BSR message from 192.168.1.2 advertising C-BSR <IP address>. (S182380)

Handling Process

<Switch>t m

<Switch>t d

<Switch>debugging pim rp

Using debug to verify why there is no RP-info by c-bsr message

Root Cause

Since the topology using direct connect and VRRP virtual IP address as gateway, so when RPF check the unicast routing table and its out-going interface, the next-hop address if not match the IP address on C-BSR message advertised by the peer physical IP, it will fail.In most example on multicst routing PIM, it will always using dynamic routing protocol instead of static route with VRRP.



Solution

Add specific RFP static-routes to VRRP master & VRRP standby next-hop physical address to ensure reachable to C-BSR IP address, so that it can pass the RPF check then accept the C-BSR message.


ip rpf-route-static <C-BSR IP> <Mask> <Physical ip address of next hop in you unicast routing table>

ip rpf-route-static <C-BSR IP> <Mask> <Physical ip address of next hop in you unicast routing table> <perference for standby next-hop>


Example:

ip rpf-route-static 192.168.3.1 32 192.168.1.2

ip rpf-route-static 192.168.3.1 32 192.168.1.3 70



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