Many thanks for the reply, but I still don’t understand what I’m missing.
I used this lab in GNS3 as displayed by the image, which I build from the ENARSI topology (pg 672 figure 17-1). But I changed the EIGRP process to ripv2 like in the networklessons lesson.
I advertised on the ASBR the 188.8.131.52/32 network via rip with a metric of 5. Then on R1 I advertise the rip routes into the OSPF process, no route-maps applied yet.
On R2 I advertise OSPF networks into rip again, with a lower metric of 1, so they are prefered in the RIP area.
The expected happens, and R3 ‘show ip route’ output says that the 184.108.40.206/32 network is via R2. Also R1 and R2 point to each other as the next hop for 220.127.116.11/32 via the OSPF interfaces.
Then I applied a route-map on R1 which sets a tag of 10 on routes redistributed from RIP to OSPF. On R2 I applied a route-map on the redistribute command that denies the redistribution of OSPF-learned routes into RIP with a tag of 10.
R3 now points to the ASBR again for the 18.104.22.168/32 network. But R2 still points to R1 via its OSPF interfaces for the 22.214.171.124/32 route, as expected.
So in my lab that routing loop is not solved, as mentioned by Rene in the lesson.
In the end further measures should be taken to fix the routing loop (suboptimal routing in my case) between R1 and R2. Like changing the AD.
Changing the AD instead
When I use don’t use route-maps, but set the distance of rip as 109 (lower then OSPF 110) on R2, R2 prefers R3 as the next-hop again for the 126.96.36.199/32 network.
And because the 188.8.131.52/32 route is in the routing table as a RIB route, and not anymore as an external OSPF route, the route will not be redistributed from OSPF into RIB and thus not being advertised to R3.
So I still don’t understand how in this scenario route-tagging could be of use, as changing the AD is necessary anyways and it solves both problems at once making route-tagging redundant. I just did this in a lab and no suboptiomal routing/loops occur, just by changing the AD.
I just read your answer a bit better, and I think your saying that in this scenario changing the AD indeed solves everyting, but this scenario is used for displaying route-tagging, not for displaying a scenerio were it’s crucial?
If that’s the case do you know a situation were route-tagging shows it true merrit?
Apologies for the long reply.