Mutual Redistribution

[miracle_david@yahoo.com]

I saw explanation about "Mutual Redistribution" in the following URL " https://www.cisco.com/c/en/us/support/docs/ip/open-shortest-path-first-ospf/7039-1.html?dtid=osscdc000283#t24 ". I didn't understand about the loop problem. Can anybody assist me figuring it out please.

Thanks in advance

[Jon Marshall]

Which bit did you not follow ? 

Bear in mind although not shown RTA will have a route for the 203.250.15.128/26 subnet pointing to RTC so if RTC uses the route pointing to RTA for this subnet you now have a routing loop. 

Jon

[Mathias Garcia]

It's a somewhat contrived problem.

I feel that it's not the best way to inform you about the possible problems with mutual redistribution. 

What is happening here is that they are lazy with the command that enables RIP (and OSPF) and so it's enabled on both the Ethernet and serial interfaces. And with that done they did not use RIP passive interface for E0 on RTA (but did do it on RTC)

So RTA learns about the 203.250.15.128 network via OSPF from RTC and then send it via RIP back to RTC. RTC has RIP as passive on E0, so it will not send out updates on that interface, but still listen for them. 

Therefore RTC think that it has 2 equal cost paths to the network 203.250.15.128 but one of them is a loop.