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Cisco Bug: CSCvs85845 - Cat9K unexpectedly forwarding Unicast Routing Protocol packets (BGP keepalives/OSPF).

Last Modified

Sep 01, 2020

Products (1)

  • Cisco Catalyst 9300 Series Switches

Known Affected Releases


Description (partial)

Cat9K switch receives a Unicast Routing Protocol packet (BGP keepalive) that is destined to IP/MAC address of the switch's vlan interface.
The switch then unexpectedly forwards/floods the Unicast Routing Protocol packet (BGP keepalive) to other ports in the same vlan.
The BGP keepalive packet is unicast and destined to Cat9K vlan interface, therefore it should not be flooded on other ports in the vlan.

Cat9K switch is using a vlan interface for the BGP peering and has other ports (trunk/access) assigned to the same vlan.

Issue can also be seen with unicast OSPF packets (static neighbor).

Issue was observed on ios versions 16.9.2 and 16.9.4, but may be present on other versions.
Issue was observed on 9300 platform, but may be present on other 9K platforms.

Behavior is easily recreated in the lab.
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