RIP v2 updates

[jinkazama_2]

Hi guys,

When turning on "debeug ip rip" , why in the RIPv2 traps are the next hop and route tag fiels all set to 0 in the updates? e.g

RIP: sending v2 update to 224.0.0.9 via Ethernet2 (172.25.150.225)

172.25.150.32/28 - 0.0.0.0, metric 2, tag 0

Many Thanks

Omid

[vijayasankar]

Hi,

If next hop is set to 0.0.0.0, it indicates that the forwarding IP address (the next hop) for that route is assumed to be the source IP address of the router which is advertising the routing update.

In this case, the next hop for the destination 172.25.150.32/28 is the originating router itself

-VJ

[jinkazama_2]

Thanks VJ,

So the router is basically just advertising these networks as being reachable through itself, which is why they are included in the RIP updates.

Do you know why RIPv1 traps dont include this information? e.g

network 172.25.0.0, metric 1

Thanks

Omid

[mahmoodmkl]

Hi

I think this is due to RIPv1 being a classful protocol.

Thanks

Mahmood

[vijayasankar]

Hi Omid,

In RIP V1 packet format specification, there is no field available to carry the next hop.

Simply RIP V1 packets dont carry the next hop information, they only carry the metric for the network advertised.

Only in RIP V2 packet format specification, we have field "next-hop" to represent the next hop information.

Have a look at this URL for RIP packet formats specification

http://cisco.com/en/US/tech/tk1330/tsd_technology_support_technical_reference_chapter09186a0080759842.html#wp1020570

Hope this helps.

-VJ