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OPERATIONAL DEFECT DATABASE
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BGP path shows up twice or more on the "show bgp " output if the soft-reconfiguration inbound is configured on one neighbor that also has an inbound route-map modifying the path. The modified path will appear more than once. Note in the examble below that paths 1 and 2 are identical: BGP routing table entry for 20.20.20.0/24, version 3 Paths: (3 available, best #2, table default) Not advertised to any peer Refresh Epoch 1 11 10.10.10.11 from 10.10.10.11 (10.10.10.11) Origin incomplete, metric 0, localpref 200, valid, external rx pathid: 0, tx pathid: 0 Updated on Oct 13 2023 15:39:23 EST Refresh Epoch 1 11 10.10.10.11 from 10.10.10.11 (10.10.10.11) Origin incomplete, metric 0, localpref 200, valid, external, best rx pathid: 0, tx pathid: 0x0 Updated on Oct 13 2023 15:39:54 EST Refresh Epoch 1 11, (received-only) 10.10.10.11 from 10.10.10.11 (10.10.10.11) Origin incomplete, metric 0, localpref 100, valid, external rx pathid: 0, tx pathid: 0 Updated on Oct 13 2023 15:39:23 EST uut# Additionally, if the path that is duplicated is withdrawn from the peer, only one duplicate is removed, and the other duplicates and received-only path remain: (peer withdraws 20.20.20.0/24) uut#sh ip bgp 20.20.20.0 BGP routing table entry for 20.20.20.0/24, version 3 Paths: (2 available, best #1, table default) Not advertised to any peer Refresh Epoch 1 11 10.10.10.11 from 10.10.10.11 (10.10.10.11) Origin incomplete, metric 0, localpref 200, valid, external, best rx pathid: 0, tx pathid: 0x0 Updated on Oct 13 2023 15:39:54 EST Refresh Epoch 1 11, (received-only) 10.10.10.11 from 10.10.10.11 (10.10.10.11) Origin incomplete, metric 0, localpref 100, valid, external rx pathid: 0, tx pathid: 0 Updated on Oct 13 2023 15:39:23 EST uut# Furthermore, for every time "clear ip bgp * soft" is executed, an additional duplicate path is seen uut#clear ip bgp * soft uut#clear ip bgp * soft uut#clear ip bgp * soft uut#sh ip bgp 20.20.20.0 BGP routing table entry for 20.20.20.0/24, version 6 Paths: (5 available, best #4, table default) Flag: 0x8200 Not advertised to any peer Refresh Epoch 1 11 10.10.10.11 from 10.10.10.11 (10.10.10.11) Origin incomplete, metric 0, localpref 200, valid, external rx pathid: 0, tx pathid: 0 Updated on Oct 13 2023 15:39:54 EST Refresh Epoch 1 11 10.10.10.11 from 10.10.10.11 (10.10.10.11) Origin incomplete, metric 0, localpref 200, valid, external rx pathid: 0, tx pathid: 0 Updated on Oct 13 2023 15:42:22 EST Refresh Epoch 1 11 10.10.10.11 from 10.10.10.11 (10.10.10.11) Origin incomplete, metric 0, localpref 200, valid, external rx pathid: 0, tx pathid: 0 Updated on Oct 13 2023 15:42:23 EST Refresh Epoch 1 11 10.10.10.11 from 10.10.10.11 (10.10.10.11) Origin incomplete, metric 0, localpref 200, valid, external, best rx pathid: 0, tx pathid: 0x0 Updated on Oct 13 2023 15:42:24 EST Refresh Epoch 1 11, (received-only) 10.10.10.11 from 10.10.10.11 (10.10.10.11) Origin incomplete, metric 0, localpref 100, valid, external rx pathid: 0, tx pathid: 0 Updated on Oct 13 2023 15:39:23 EST uut#
- Configure neighbor with soft-reconfiguration inbound. - Configure neighbor with inbound route-map that modifies a BGP attribute. (neighbor x.x.x.x route-map in) Example: Ex: uut config: route-map MAP permit 10 set local-preference 200 ! router bgp 10 neighbor 10.10.10.11 remote-as 11 neighbor 10.10.10.11 soft-reconfiguration inbound neighbor 10.10.10.11 route-map MAP in !
Disable soft-reconfiguration inbound or remove the inbound route-map. Note: the route-map only affects if it has a "set" statement, match-only route-maps do not cause this issue
Caused by CSCwf47257 bug fix Impact of this bug involves: -Higher memory utilization for the additional duplicate paths created. -Traffic can be black-holed, since the paths are not deleted after receiving a withdraw, and these stale paths continue to be selected as bestpaths