Route selection with BGP not working as expected

You must have a route-map to raise the local preference to 200 (default 100) for the routes from 10.29.127.5 neighbor. Local preference has higher priority than AS path.

Toshi

Hi @ksmithaz1,

Welcome to the community.

Can you share the BGP configuration?

Looking at your output:

home-gw # get router info bgp network 10.31.1.0/24
VRF 0 BGP routing table entry for 10.31.1.0/24
Paths: (2 available, best #1, table Default-IP-Routing-Table)
Advertised to non peer-group peers:

10.10.1.1

Original VRF 0
65497 4200090001 4200090001 4200090001
10.29.127.5 from 10.29.127.5 (10.29.127.5)
Origin incomplete metric 20, localpref 200, valid, external, best
Last update: Tue Jul 19 22:26:19 2022

Original VRF 0
65495 4200090001
10.10.1.1 from 10.10.1.1 (10.29.1.1)
Origin incomplete metric 0, localpref 100, valid, external
Last update: Tue Jul 19 22:37:35 2022

We can see that the prefix received from 10.29.127.5 has a metric of 20 and localpref of 200.

BGP selects the best path based on a list of attributes:

• Weight.
• Local Preference.
• Originate.
• AS path length.
• Origin code.
• MED (metric)
• eBGP path over iBGP path.
• Shortest IGP path to BGP next hop.

In your case, based on the output, the path via 10.29.127.5 is selected because of the local preference (probably configured on home-gw and applied as route-map-in).

MED (Multi Exit Discriminator) Attribute is the BGP Path attribute which provides information to the external neighbors, about how to come their AS (probably configured on the 10.29.127.5 and 10.10.1.1 and applied, probably, as route-map-out).

Looking at the config would provide more insight.

config router bgp
   set as 65496
   set router-id 10.29.127.1
   set always-compare-med enable
   config neighbor
       edit "10.29.127.5"
           set soft-reconfiguration enable
           set remote-as 65497
           set route-map-in "RM-IANA"
           set route-map-out "RM-IANA"
       next
       edit "10.29.127.9"
           set remote-as 65409
       next
       edit "10.10.1.1"
           set ebgp-enforce-multihop enable
           set soft-reconfiguration enable
           set remote-as 65495
           set route-map-in "RM-IANA-100"
           set route-map-out "RM-IANA-100"
       next
   end
   config network6
       edit 1
           set prefix6 ::/128
       next
   end
   config redistribute "connected"
       set status enable
   end
   config redistribute "rip"
   end
   config redistribute "ospf"
   end
   config redistribute "static"
       set status enable
   end
   config redistribute "isis"
   end
   config redistribute6 "connected"
   end
   config redistribute6 "rip"
   end
   config redistribute6 "ospf"
   end
   config redistribute6 "static"
   end
   config redistribute6 "isis"
   end
end