Symptom

- When MED updates for ECMP BGP routes received from 2 eBGP peers and both are updated simultaneously, it will only update the metric in RIB for one of the paths. This leads to loss of ECMP in routing table. DCSW# sh ip bgp 8.8.8.8 BGP routing table information for VRF default, address family IPv4 Unicast BGP routing table entry for 8.8.8.8/32, version 47 Paths: (2 available, best #2) Flags: (0x08001a) (high32 00000000) on xmit-list, is in urib, is best urib route, is in HW Multipath: eBGP Path type: external, path is valid, not best reason: newer EBGP path, multipath, no labeled nexthop, in rib AS-Path: 65200 , path sourced external to AS 10.1.2.2 (metric 0) from 10.1.2.2 (10.1.2.2) Origin incomplete, MED 105, localpref 100, weight 0 <<<< Advertised path-id 1 Path type: external, path is valid, is best path, no labeled nexthop, in rib AS-Path: 65100 , path sourced external to AS 10.1.1.2 (metric 0) from 10.1.1.2 (10.1.1.2) Origin incomplete, MED 105, localpref 100, weight 0 Path-id 1 not advertised to any peer DCSW# sh ip route 8.8.8.8 IP Route Table for VRF "default" '*' denotes best ucast next-hop '**' denotes best mcast next-hop '[x/y]' denotes [preference/metric] '%' in via output denotes VRF 8.8.8.8/32, ubest/mbest: 1/0 *via 10.1.2.2, [20/6], 00:07:59, bgp-65000, external, tag 65200 <<<<< via 10.1.1.2, [20/105], 00:07:59, bgp-65000, external, tag 65100

Conditions

- Receiving equal cost paths from 2 eBGP peers. - Multipath configured.

Workaround

- Clear the route "clear ip route " - Configure a route-map to set all routes received from eBGP neighbors to same MED so as to not impact ECMP.

Further Problem Description