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Cisco Bug: CSCum00578 - N5k VPC - MAC learning issue after ISSU from 5.0(3)N2(2b) to 5.2(1)N1(4)

Last Modified

Sep 13, 2017

Products (7)

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

Known Affected Releases

5.0(3)N2(2b) 5.2(1)N1(4)

Description (partial)

The MAC address of the host cannot be relearned by the unicast traffic from the host, once it is expired by inactivity timer (300s by default). This breaks the backward communication to the host.

Clearing ARP on the problematic host and sending a new one ARP request creates the MAC address entry for the host again, and it can commnuicate until the MAC address is not expired by inactivity timer (300s).

Bouncing the corresponding FEX interface to the problematic host resolves the issue for the interface.
Reloading the box resolves the issue on the entire box.

This is seen on N5k VPC system for orphan host connected to single-homed FEX device after ISSU from 5.0(3)N2(2b) to 5.2(1)N1(4).
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Bug Details Include

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