Rip again!

Sun Aug 21 16:20:50 UTC 2005

How about the source IP?

RIP v1 is sent to 255.255.255.255 broadcast.  RIPv2 is sent to 224.0.0.9
multicast.  Both are local-link only, so won't go THROUGH a router.  The
sending source IP will tell you where they came from.

If you're using VLANs (trunks), there won't be any issues.  If you're using
secondary addresses, this will depend on whose devices you use.   In the
Cisco world, packets will always be sourced from the primary IP address on
an interface.  And if the receiving router doesn't have a subnet matching
the sender, packets/updates are ignored.  (Again, Cisco world you can use
"no validate-update-source" to override this check)

But that gives you a tracking method on packets.  

Scott 

-----Original Message-----
From: owner-nanog at merit.edu [mailto:owner-nanog at merit.edu] On Behalf Of Tom
Sanders
Sent: Sunday, August 21, 2005 12:13 PM
To: nanog at nanog.org
Subject: Rip again!

Hi,

There isnt IMO a way in RIP to identify the source of the RIP packet (the
way we have Router ID in OSPF, system ID in ISIS, etc.)

Now assume we have 2 vlans defined on an ethernet. Thus we would have two IP
interfaces, 1.1.1.1/24 and 2.2.2.2/24 and both using the same physical
interface. RIP is running on both these interfaces.

My doubt is that how will another router, which is configured in the same
way (2 vlans) be able to differentiate between the RIP responses originated
by 1.1.1.1 and 2.2.2.2?

Thanks,
Toms