This senario comes form Routing TCP/IP volume 2, page 298.
When I finished configuring all 8 routers, I have the following output form the router named Whitetooth:
r6#sh ip bgp 10.35.5.0
BGP routing table entry for 10.35.5.0/24, version 14
Paths: (2 available, best #2, table Default-IP-Routing-Table)
Advertised to non peer-group peers:
10.35.255.1 (metric 782) from 10.35.255.1 (10.35.255.1)
Origin IGP, metric 0, localpref 100, valid, confed-external
10.34.255.2 (metric 782) from 10.34.255.2 (10.34.255.2)
Origin IGP, metric 0, localpref 100, valid, confed-internal, best
My question is: why confed-internal route is selected as the best rather than the confed-external one? On page 115 of the same book, the No. 7 of path selection criterion states that:
...,prefer EBGP routes over confederation EBGP routes, and prefer confederation EBGP routes over IBGP routes.
which is conflicting with my lab result.
Any idea? Thanks
there is no distinction between a confederation internal and external path (step 7 in the included URL). The second path is selected based on the fact that it has the lowest RID of both path.
Please refer to the following URL for more details on the BGP Best Path Selction process.
Hope this helps,