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Cisco Bug: CSCul52253 - VPC+ allocates ftag-1 and ftag-2 as active

Last Modified

Feb 15, 2018

Products (9)

  • Cisco Nexus 5000 Series Switches
  • Cisco Nexus 5596UP Switch
  • Cisco Nexus 5548P Switch
  • Cisco Nexus 6004 Switch
  • Cisco Nexus 6001 Switch
  • Cisco Nexus 5020 Switch
  • Cisco Nexus 5548UP Switch
  • Cisco Nexus 5596T Switch
  • Cisco Nexus 5010 Switch

Known Affected Releases

5.2(1)N1(5) 6.0(2)N2(3)

Description (partial)

Symptom:
The problem is being triggered when both vPC+ peers are becoming Primary initially due to auto-recovery.  At this point ftag-2 is activated without disabling ftag-1. 


'show fabricpath topology ftag active' affected switch
Topo-Description          Topo-ID    Graph-ID  Ftag      
------------------------- ---------- --------- ---------
0                         0          1         1         
0                         0          2         2

'show fabricpath topology ftag activ'  on the peer switch
Topo-Description          Topo-ID    Graph-ID  Ftag      
------------------------- ---------- --------- ---------
0                         0          1         1    
 
Since we have both FTAG's active we might be impacting broadcast/multicast traffic passing through the affected N5k switch.

Conditions:
This is usually seen when both switches come up as vPC primary(dual active  state when both keep-alive and peer-link are down and during switch reboot) due to vPC auto-recovery enabled.

Basically anytime the two N5ks have auto-recovery kick in because they cannot detect the peer-link and keepalive link when they bootup then we will run into this bug.
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