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Cisco Bug: CSCvv77365 - Forwarding for mac addresses in a vlan that is extended across VXLAN fabric may fail.

Last Modified

Oct 19, 2020

Products (1)

  • Cisco Catalyst 9600 Series Switches

Known Affected Releases

17.3.1

Description (partial)

Symptom:
A Cat9k switch configured with vxlan evpn may see a few different conditions as a result of this issue. 

1) Client macs may not be learned in the vlan, even when its confirmed traffic is ingressing the ports. (missing mac)

2) Traffic destined to a missing mac will not be unknown unicast flooded out the proper interfaces. 

3) Unicast traffic to macs learned over the overlay (or rarely, locally) may fail to forward properly and be silently consumed by the switch

Conditions:
Seen on Cat9k series switches for vlans that are extended across an overlay in a VXLAN or similar type solution. 

MAC addresses in question do not need to be directly learned over the overlay, traffic between two ports in the same vlan being switched locally can also be impacted.

Previously working hosts may be triggered into this broken condition after L3 SVI and/or overlay interface instability
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