what is the significance of router-id in OSPF/EIGRP/BGP?

[ramanbishnoi1]

I have used router-id and I can see the practical value of router-id in OSPF/EIGRP/BGP. 

Logically what I can understand that RID is used when there is tie between two routes than it can play role, but what about the if "RID" is not advertised in OSPF/EIGRP/BGP but rest everything is works normally?

I means to say one loopback2 is not a part of Routing Protocol but locally highest loopback address and configured as router-id manually (if only), what will be the impact ?

[e.ciollaro]

Hi

i don't understand what you mean with

if "RID" is not advertised in OSPF/EIGRP/BGP but rest everything is works normally?

In any case RID is not just a tie breaker, in BGP e EIGRP it is also used to avoid routing loops or routing feedbacks. In EGIRP it is used in case of external routes: when a router receives an external route, it checks if the RID is different form its own RID; if not, the advertisement is discarded. Something similar happen in BGP when you use route reflector (in the case the Cluster ID by default is equal to RID).

Bye,

enrico