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Cisco Bug: CSCuo76751 - Port asic in shared mode does not set Don't_fwd and Don't_learn bit

Last Modified

Jul 17, 2019

Products (8)

  • Cisco Nexus 7000 Series Switches
  • Cisco Nexus 7000 10-Slot Switch
  • Cisco Nexus 7000 4-Slot Switch
  • Cisco Nexus 7700 6-Slot Switch
  • Cisco Nexus 7000 18-Slot Switch
  • Cisco Nexus 7700 18-Slot Switch
  • Cisco Nexus 7000 9-Slot Switch
  • Cisco Nexus 7700 10-Slot Switch

Known Affected Releases

6.2(8) 6.2(8)S25

Description (partial)

Symptom:
Symptom 1: Port-channel member interfaces go into an LACP suspended state b/c because they stop sending LACP PDUs. 
Symptom 2: Ports may stop learning mac addresses and stop passing traffic
Symptom 3: Ports may stop learning mac addresses but still flood traffic

Conditions:
Symptom 1 & 2 can be seen when a span destination is configured on a port M132 port in shared mode.  Other ports in the port-group will set the DL (Don't Learn) and DF (Don't Forward) bit set to ON. 
N7K# slot 1 sho hard int mac port 26 state | egrep  -i "dont"
                dont_forward: ***On***, dont_learn: ***On***

Symptom 3 is seen when the peer-link is on a shared-mode M132 port.  MAC learning is disabled on the peer-link by default.  Configuring a peer-link member interface on a shared-mode M132 port will disable MAC learning on the other three ports in the port-group. 
N7K# slot 1 sho hard int mac port 26 state | egrep  -i "dont"
                dont_forward: Off, dont_learn: ***On***

These conditions may be triggered by reloading a VDC or flapping an interface (the VDC reload results in a link flap, the link flap triggers the error condition), though it has been seen when no link flap could be confirmed. When the VDC reload is complete the links in the port channel remain in the suspended state since LACP PDUs are not forwarded.
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