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Cisco Bug: CSCvs03903 - Member add to existing bundle causes traffic drop due to index collision based on instance & port

Last Modified

Jul 28, 2020

Products (11)

  • Cisco ASR 9000 Series Aggregation Services Routers
  • Cisco ASR 9910 Router
  • Cisco ASR 9922 Router
  • Cisco IOS XR Software
  • Cisco ASR 9010 Router
  • Cisco ASR 9904 Router
  • Cisco ASR 9006 Router
  • Cisco ASR 9901 Router
  • Cisco ASR 9001 Router
  • Cisco ASR 9912 Router
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Known Affected Releases

6.4.2.BASE

Description (partial)

Symptom:
Member add to exsisting bundle causes traffic drop due to index collision based on instance & port

Conditions:
This is a reproducible issue on ASR9k 

Index is colliding for multiple interfaces, because of calculation based on instance and port. 
 
During Attach, port is provided by NP lib and same is used to calculate index for Port IFH array. Below index 20 is same for 0/3/0/1/4 and 0/3/1/0/0. Interfaces incrementally will have same collision. Hence we see the issue for patterns mentioned earlier. Attached debug logs collected.
 
Sub X MAX + port = INDEX
 
 
0  x 20 + 17 = 17   <——— Ten 0/3/0/1/1
0  x 20 + 18 = 18   <——— Ten 0/3/0/1/2
0  x 20 + 19 = 19   <——— Ten 0/3/0/1/3
0  x 20 + 20 = 20   <——— Ten 0/3/0/1/4
 
—
 
1  x 20 + 0 = 20   <——— Ten 0/3/1/0/0
1  x 20 + 1 = 21   <——— Ten 0/3/1/0/1
1  x 20 + 2 = 22   <——— Ten 0/3/1/0/2
1  x 20 + 3 = 23   <——— Ten 0/3/1/0/3
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