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Cisco Bug: CSCvs72056 - Traffic blackhole after core interface flap

Last Modified

Sep 24, 2020

Products (12)

  • Cisco ASR 9000 Series Aggregation Services Routers
  • Cisco Network Convergence System 5504
  • Cisco Network Convergence System 55A2-MOD-HD-S
  • Cisco Network Convergence System 5502-SE
  • Cisco Network Convergence System 5516
  • Cisco Network Convergence System 55A1-24H
  • Cisco Network Convergence System 5502
  • Cisco Network Convergence System 55A2-MOD-S
  • Cisco Network Convergence System 55A2-MOD-SE-S
  • Cisco Network Convergence System 5501-SE
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Known Affected Releases

6.6.2.BASE 6.6.3.BASE 7.1.1.BASE

Description (partial)

Symptom:
Traffic blackhole after flap on core interface.

Conditions:
Have VPNV4 NH learned via IBGP inside the vrf.

RP/0/RP0/CPU0:F340.13.21-NCS55A2-2#show route vrf INTERNET
Fri Jan 17 16:16:10.970 UTC

Codes: C - connected, S - static, R - RIP, B - BGP, (>) - Diversion path
       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
       E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
       i - ISIS, L1 - IS-IS level-1, L2 - IS-IS level-2
       ia - IS-IS inter area, su - IS-IS summary null, * - candidate default
       U - per-user static route, o - ODR, L - local, G  - DAGR, l - LISP
       A - access/subscriber, a - Application route
       M - mobile route, r - RPL, t - Traffic Engineering, (!) - FRR Backup path

Gateway of last resort is not set

B    6.6.6.6/32 [200/0] via 5.5.5.5 (nexthop in vrf default), 02:27:52    <<-- next-hop for vpnv4 route learned via ibgp
S    7.7.7.7/32 [1/0] via 10.0.47.7, 10:23:19
C    10.0.47.0/24 is directly connected, 10:23:19, TenGigE0/0/0/6
L    10.0.47.4/32 is directly connected, 10:23:19, TenGigE0/0/0/6
L    14.14.14.14/32 is directly connected, 10:23:48, Loopback100
B    15.15.15.15/32 [200/0] via 5.5.5.5 (nexthop in vrf default), 02:27:52
B    172.16.1.0/24 [200/0] via 7.7.7.7, 01:56:07
B    200.4.0.0/24 [200/0] via 6.6.6.6, 01:55:59   <-- affected network

5.5.5.5/32 is learned via IGP on default vrf.  It can happen with static route as well.
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Bug Details Include

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