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Cisco Bug: CSCvv14062 - NEXUS 3548 MTC has IP unicast reachability from Sup to any direct connect end host

Last Modified

Oct 09, 2020

Products (1)

  • Cisco Nexus 3000 Series Switches

Known Affected Releases

7.0(3)I7(8) 9.3(5)

Description (partial)

One of the Neuxs 3548 across vPC peer-link can not reach the direct connected host behind the vPC port-channel. All IP unicast traffic that generated from CPU is involved. L2 traffic , L3 multicast and L3 broadcast works fine. We do see ARP is resolved and HSRP works fine.L2 forwarding for data packet that came outside the switch to the impact port-channel is also fine

TX counter did not increase for the impact Port-channel when we send the ping

LCND show INVALID packet and it constantly increasing.

Symptom:
One of the Nexus across vPC is not reachable to direct connected device. All Control-plane generated IP unicast packet are impacted.  L2 forwarding is fine on data plane. TX counter never increased.

Conditions:
Two vPC domain interconnect via back to back vPC setup. All four device across two peer-link are nexus 3548. For each domain, Multiple sever and few network device are directly connected via vPC port-channel to each of the Nexus. The issue is triggered after  downgrade from 9.3.3 to i7(8). Upgrade to 9.3.5 will not help.  Only host devices are impacted
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