Cisco Support Community
cancel
Showing results for 
Search instead for 
Did you mean: 
Announcements

Welcome to Cisco Support Community. We would love to have your feedback.

For an introduction to the new site, click here. If you'd prefer to explore, try our test area to get started. And see here for current known issues.

New Member

bgp bestpath confusion

Hi all,

I have the following result when i do show ip bgp

R1#sh ip bgp

BGP table version is 2, local router ID is 1.1.1.1

Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,

              r RIB-failure, S Stale

Origin codes: i - IGP, e - EGP, ? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path

* i2.2.2.2/32       10.1.24.2                0    100      0 200 i

*>i                 10.1.23.2                0    100      0 200 i

R1#

I can see that best path is selected from 10.1.23.2 (coming from R3). Is there any debug or show command that can tell me exactly on which step does the best path was selected ? like was it selected on local pref or something else

Everyone's tags (1)
3 REPLIES
Hall of Fame Super Silver

bgp bestpath confusion

Hello Jonn,

to see more details of the two BGP advertisements you can use

show ip bgp 2.2.2.2

From the show that you have reported the two paths have:

same weight 0

same local preference 100 (default)

same AS path length  200

same origin code i (internal)

same MED 0

both paths are learned via an iBGP session that is given by the leftmost *i or *>i

the second path is the best ( > character) but we cannot see why.

The likely criteria involved are :

lowest IGP metric to BGP next-hop

lowest BGP router-id

You can see these missing details in the show ip bgp 2.2.2.2 including eventually cluster-list and originator-id if RR servers are in use.

Hope to help

Giuseppe

New Member

bgp bestpath confusion

Sorry Sir i didnt pasted the result of show ip bgp 2.2.2.2 but it's also not showing anything that can help me understand at exact which step does the decision was made. Basically i wanted to ask that is there any show/debug command that can tell me exact step of decision or there is no such thing ?

Hall of Fame Super Silver

bgp bestpath confusion

Hello Jonn,

feel free to post the show ip bgp 2.2.2.2 and I will try to comment on it

Hope to help

Giuseppe

475
Views
0
Helpful
3
Replies