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Cisco Bug: CSCum46326 - ASR9k IPv6 CEF broken for bundle subintf if local & remote

Last Modified

Nov 27, 2020

Products (1)

  • Cisco ASR 9000 Series Aggregation Services Routers

Known Affected Releases

4.3.1.BASE 5.1.0.BASE

Description (partial)

Symptom:
Routing to a previously attached network via a IGP (OSPF is known to be broken), will fail due to CEF thinking the route is still attached:

Both of these subnets are directly connected to ASR9006-E, after interface bundle-E21.21 is shutdown, ASR9006-E should learn this route from a neighbor

Bundle-E20.20 -- FC00:0:0:20::/64
Bundle-E21.21 -- FC00:0:0:21::/64

RP/0/RSP0/CPU0:ASR9006-E#show route ipv6

[output omitted]

C   fc00:0:0:20::/64 is directly connected,
      01:06:47, Bundle-Ether20.20

L    fc00:0:0:20::1/128 is directly connected,
      01:06:47, Bundle-Ether20.20

C   fc00:0:0:21::/64 is directly connected,
      01:13:15, Bundle-Ether21.21

L    fc00:0:0:21::1/128 is directly connected,
      01:13:15, Bundle-Ether21.21

This is what the routing table looks like after Bundle-e21.21 is shutdown:

RP/0/RSP0/CPU0:ASR9006-E#show route ipv6

[output omitted]

C   fc00:0:0:20::/64 is directly connected,
      01:12:33, Bundle-Ether20.20

L    fc00:0:0:20::1/128 is directly connected,
      01:12:33, Bundle-Ether20.20

O   fc00:0:0:21::/64 is directly connected,
      00:03:47, Bundle-Ether20.20

The route is now learned from the neighbor over a different bundle; however, we cannot route to this subnet, as CEF reports the subnet is 'attached' and 'glean'.

RP/0/RSP0/CPU0:ASR9006-E#show cef ipv6 fc00:0:0:21::
fc00:0:0:21::/64, version 223, attached, glean adjacency, internal 0x4000081 (ptr 0x71cb9954) [1], 0x0 (0x7151bac0), 0x0 (0x0)
 Updated Jan  8 18:04:11.523
 Prefix Len 64, traffic index 0, precedence n/a, priority 2
   via Bundle-Ether20.20, 4 dependencies, weight 0, class 0 [flags 0x8]
    path-idx 0 [0x71036500 0x0]
     glean adjacency

Conditions:
* IPv6
* Route was previously Connected and Local
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