what would you do to check routing table stability, to check there is no loop in the network
You have two options:
1. "debug ip routing" and see if routes are being constantly added and removed to the global RIB (take note that if you run RIP you will see routes will be constantly added to the global RIB, each update interval, because the route needs to be refreshed in RIP).
2. enable "ip route profile" and look at "show ip route profile" to note the same thing as in option 1.
But the fact that the router has its routing table to be stable, does NOT mean there is no loop in the network, with a bad config you can make that happen; this is when the loop is permanent.
thanks a lot cristian.matei for your answer
Those sound like two different things. Route table stability can have numerous factors associated with it. Flapping links, failure to converge, misconfigurations etc etc. The first thing I like to look at is the age of a route.
Ex. show ip routeB 10.3.0.0/24 [20/100] via 220.127.116.11, 5d19h [20/100] via 10.250.4.129, 5d19h
I've known about those two routes for nearly 6 days. Now if someone were to tell me there as an *insert issue here* 6 days ago, the routing table is one of the more obvious ways of showing that next to looking at the syslogs.
Something like a loop would be evident with a traceroute typically.