Interface down on Cisco Nexus switch with “dcxNoACKi”

Cisco, Linux, Netwoking / By /

Problem: After an update of a server to Devuan4/Debian11the switch shuts down the interfaces to the server with status “dcxNoACKi” 48 minutes after the reboot.

Discussion: the switch is a Cisco Nexus 5000 switch. It implements “Data Center Bridging Capability Exchange (DCBX)”. The server is a Dell server with X710 Controller 10GbE with i40e drivers. It seems that the server sends these DCBX packets during reboot, but does not answer these packages from the running OS. The switch warns for some time and then shuts down the interface:

2023 Sep  3 22:09:24 IX7 %ETHPORT-5-IF_UP: Interface Ethernet1/4 is up in mode access
2023 Sep  3 22:12:28 IX7 %LLDP-1-NO_DCBX_ACKS_RECV_FOR_LAST_10_PDUs: No Acks have been received on Interface Eth1/4 for last 10 DCBX PDUs
2023 Sep  3 22:17:27 IX7 %LLDP-1-NO_DCBX_ACKS_RECV_FOR_LAST_10_PDUs: No Acks have been received on Interface Eth1/4 for last 20 DCBX PDUs
....
2023 Sep  3 22:57:49 IX7 %ETHPORT-5-IF_DOWN_NONE: Interface Ethernet1/4 is down (None)
2023 Sep  3 22:57:49 IX7 %ETHPORT-5-IF_DOWN_ERROR_DISABLED: Interface Ethernet1/4 is down (Error disabled. Reason:DCX-No ACK in 100 PDUs)

# show interface status
Eth1/1        Servername Ext       dcxNoACKi 10        full    10G     SFP-H10GB-C

Solution: Workarround: You can disable LLDP on the switch as an Cisco article suggests, if you don’t need it for FiberChannel or similar.

N5k(config)# interface E1/1
N5k(config-if)# no lldp receive
N5k(config-if)# no lldp transmit

Source: https://www.cisco.com/c/en/us/support/docs/switches/nexus-5000-series-switches/116249-troubleshoot-nexus-00.html