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Cisco Bug: CSCum05295 - BGP multipath entry in uRIB does not get updated after attribute change

Last Modified

May 11, 2020

Products (4)

  • Cisco Nexus 7000 Series Switches
  • Cisco Nexus 7000 10-Slot Switch
  • Cisco Nexus 7000 18-Slot Switch
  • Cisco Nexus 7000 9-Slot Switch

Known Affected Releases

6.1(1)

Description (partial)

Symptom:
There are two symptoms that can be seen for this bug.

1. The following error message can be seen in syslog and IGP redistributing BGP routes may fail.

2013 Dec 13 01:21:58 PTAINTS410 %OSPF-3-RPM_LIB_API_FAILED: bgp_lookup_ext_attr() - failed in rpm_acquire_bgp_shmem_lock()

2. A route with a stale metric in the routing table exists

`DC1-CORE-3#  sho ip bgp 10.10.63.0

BGP routing table information for VRF default, address family IPv4 Unicast
BGP routing table entry for 10.10.63.0/25, version 127677
Paths: (6 available, best #1)
Flags: (0x00001a) on xmit-list, is in urib, is best urib route
Multipath: eBGP iBGP

<snip>
  Path type: internal, path is valid, received and used, not best reason: Router Id, multipath
  AS-Path: NONE, path sourced internal to AS
    1.1.2.3 (metric 101) from 1.1.2.3 (1.1.2.3)
      Origin IGP, MED 409, localpref 100, weight 0  <====== MED 409 should match routing table


DC1-CORE-3# sho ip route 10.10.63.0
IP Route Table for VRF "default"
'*' denotes best ucast next-hop
'**' denotes best mcast next-hop
'[x/y]' denotes [preference/metric]
'%<string>' in via output denotes VRF <string>

10.10.63.0/25, ubest/mbest: 5/0
    *via 1.1.2.2, [200/409], 00:10:12, bgp-65001, internal, tag 65001
    *via 1.1.2.5, [200/409], 00:43:22, bgp-65001, internal, tag 65001
    *via 1.1.2.6, [200/409], 00:43:22, bgp-65001, internal, tag 65001
    *via 1.1.2.7, [200/409], 00:43:22, bgp-65001, internal, tag 65001
    *via 1.1.2.8, [200/409], 00:43:22, bgp-65001, internal, tag 65001
     via 1.1.2.3, [200/65940], 00:15:17, bgp-65001, internal, tag 65001 <<======= OLD MED 409 not updated

Conditions:
1. IGP (e.g., OSPF) redistributes BGP routes.
2. The redistribution uses route-map to evaluate community associated with the routes.
3. Maximum-paths command is configured.
4. BGP receives paths with only attribute (e.g., AS-PATH,MED) change.
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