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lildevil

join:2003-04-28
West Lafayette, IN

Routing - is there something blocking this?

Say you have Router B that is running bgp (neighbor to Router A from one interface) and running eigrp with a neighbor to Router C at another interface. Redistribution occurs both ways (bgp to eigrp and eigrp to bgp). What I noticed is that if the middle Router B receives a eBGP route (say 10.10.10.0/24) and it also sees the same route coming via EIGRP, it will insert the BGP route and redistribute into EIGRP but ignores the EIGRP route (won't redistribute into BGP). Is this due to router trusting a BGP route more and inherently drops the IGP type route and if so is there a way to override this?


Da Geek Kid

join:2003-10-11
::1
kudos:1
Reviews:
·Callcentric
Generally it is a bad design to redistribute without tagging... This is because there could possibly be a loop in your routing design...

eBGP has a lower admin distance.

Connected interface 0

Static route 1

Enhanced Interior Gateway Routing Protocol (EIGRP) summary route 5

External Border Gateway Protocol (BGP) 20

Internal EIGRP 90

IGRP 100

OSPF 110

Intermediate System-to-Intermediate System (IS-IS) 115

Routing Information Protocol (RIP) 120

Exterior Gateway Protocol (EGP) 140

On Demand Routing (ODR) 160

External EIGRP 170

Internal BGP 200

aryoba
Premium,MVM
join:2002-08-22
kudos:6
reply to lildevil
If the BGP route has lower administrative distance, then the same route learned from different source with higher administrative distance will be ignored. You can verify this by checking the Router B's BGP Table (show ip bgp command on Cisco router).

The bigger question from my perspective is why and how does Router B learn the same route from multiple sources? If you are trying to have some kind of redundancy, then careful network design should be considered to avoid confusion and routing instability.

nosx

join:2004-12-27
00000
kudos:5
General rule of thumb for the lazy and stupid (e.g. me) if it doesnt get installed in the routing table, it doesnt get redistributed from one protocol into another. Reasoning for why the eBGP route is better and thus the one installed in the routing table (admin distance) was pointed out by previous replies. The logic being why would i tell someone else about a route that i dont think is good enough to use?