I am running multiple Protocols on different Routers as so:
- R1-RIPv2 EIGRP OSPF
- R2-OSPF and RIPv2
- R3-RIPv2 and EIGRP
- R4-EIGRP and OSPF
This is not a practical exercise, it is just to explore how different protocols may take precedence over other protocols and how to manipulate the routing table. Usually you run a single protocol, so I never thought about this until this scenario came up.
R2 learned through RIPv2 about network 126.96.36.199 on the loopback of R3. I always assumed the information came from the direct neighbor, in this case R1. The update did take that path, and R1 has a RIPv2 database of course but most of the routes on R1 were learned through EIGRP (D), but one, R2 188.8.131.52 was learned through OSPF because R2 isn't running EIGRP. This is important to my question so keep it in mind please for just a moment. R2 learned about 184.108.40.206 (R3) through RIPv2. I was under the impression the routes are exchanged by direct neighbors, so that it would have to learn about R3 220.127.116.11 from R1, but R1 has no RIPv2 routes in its table, the route was learned through the g0/0/1 interface on R2 which is 10.1.1.2 on the image. So did R3 send that information through R1 to R2 or did R1 access that from its RIP database and send the information. Which I can't fathom. If it did come from R1 I would expect it would have been exchanged with OSPF as it is a better AD than RIP, which is why I suspect it was learned from other RIP Routers or in this case R3? Can someone clarify, as I said my assumptions were based on all routers running the same protocol which made it easy to believe the neighbor router updates it's neighbors because of the path the update takes. RIP is a routing by rumour protocol is it not. SO I am confused as to how R2 learned about R3 loopback 18.104.22.168