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Cisco Bug: CSCvu07746 - packets are getting dropped when number of ECMP/UCMP paths is bigger than 32 on BVI to GRE

Last Modified

Sep 02, 2020

Products (11)

  • Cisco ASR 9000 Series Aggregation Services Routers
  • Cisco ASR 9910 Router
  • Cisco IOS XR Software
  • Cisco ASR 9922 Router
  • Cisco ASR 9010 Router
  • Cisco ASR 9904 Router
  • Cisco ASR 9006 Router
  • Cisco ASR 9901 Router
  • Cisco ASR 9001 Router
  • Cisco ASR 9906 Router
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Known Affected Releases

6.5.3.BASE

Description (partial)

Symptom:
Some of the packets are dropped in the UCMP/ECMP scenario with more than 32 paths where ingress interface is BVI and one of the egress interfaces is GRE Tunnel (Tunnel-IP interface).

Packets are being dropper on the ingress LC on the following NPU counter: RSV_DROP_IPV4_TXADJ_NO_MATCH.

show cef drops location <loc> command is reporting "No route drops" on ingress LC:

For example:

RP/0/RSP0/CPU0#show cef drops location 0/2/CPU0
CEF Drop Statistics
Node: 0/2/CPU0
  Unresolved drops     packets :               0
  Unsupported drops    packets :               0
  Null0 drops          packets :               0
  No route drops       packets :               4230  <- drops reported.

Conditions:
Issue is visible when following conditions are met:
- Ingress interface is BVI
- Traffic is load-balanced over more than 32 ECMP/UCMP paths
- One of the egress interfaces is Tunnel-IP
- Ingress LC / NPU is different than Egress one

Additional trigger:
- Features like ACL, Netflow configured on BVI which is triggering slow path processing
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Bug Details Include

  • Full Description (including symptoms, conditions and workarounds)
  • Status
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  • Known Fixed Releases
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