bgp multipath duplicate kernel routes

Leonardo Porto leonardo.porto at iw.net.br
Fri Oct 28 19:11:49 UTC 2022


Hi everyone,

I have a new FRR instalation on Rocky Linux and realized I have 
duplicate kernel routes for same-cost received routes from two distint 
peers.
It seems to be a default multipath behavior (the router shares the 
traffic indeed) but I would like to disable it and I could not find out how.
Can you guys give me any tips?

[router]# vtysh -c "show ip bgp X.Y.Z.0/22" BGP routing table entry for 
X.Y.Z.0/22, version 15072201 Paths: (2 available, best #2, table 
default)   Not advertised to any peer   Local     A.B.144.30 from 
A.B.144.5 (A.B.144.30)       Origin IGP, metric 0, localpref 100, valid, 
internal, multipath       Originator: A.B.144.30, Cluster list: 
A.B.144.1       Last update: Fri Oct 28 03:16:08 2022   Local     
C.D.113.30 from C.D.113.5 (A.B.144.30)       Origin IGP, metric 0, 
localpref 100, valid, internal, multipath, best (Neighbor IP)       
Originator: A.B.144.30, Cluster list: C.D.113.1       Last update: Fri 
Oct 28 03:16:01 2022 # [router]# ip route show X.Y.Z.0/22 X.Y.Z.0/22 
proto bgp metric 20         nexthop via C.D.113.5 dev eth0.1001 weight 1 
         nexthop via A.B.144.5 dev eth0.1001 weight 1

The workaround is to apply local-pref.

Rocky Linux release 8.6 4.18.0-372.26.1.el8_6.x86_64
FRRouting (version 8.3.1)

Leonardo

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