Symptom

BFD Multihop support was added for Nexus 9000 and limited Nexus 3000 platforms as of 9.2(1). In situations where a customer needs to downgrade back to a lower release, this will fail the multihop configuration pre-check due to having an active BFD session registering as a Multihop session as listed below: N3K-1# install all kickstart bootflash:n3500-uk9-kickstart.6.0.2.A8.3.bin system n3500-uk9.6.0.2.A8.3.bin no-save bios-force Installer will perform compatibility check first. Please wait. Installer is forced disruptive Verifying image bootflash:/n3500-uk9-kickstart.6.0.2.A8.3.bin for boot variable "kickstart". [####################] 100% -- SUCCESS Verifying image bootflash:/n3500-uk9.6.0.2.A8.3.bin for boot variable "system". [####################] 100% -- SUCCESS Notifying services about system upgrade. [# ] 0% -- FAIL. Return code 0x420E0085 (Multihop configuration check failed. Please remove multihop commands before proceeding to downgrade). <<< Service "bfd" in vdc 1: Multihop BFD is not supported in the target version on this hardware. <<< Please remove all Multihop BFD related configs and sessions. Use "show running-config bfd" and delete Multihop BFD related config.Aborting downgrade. Pre-upgrade check failed. Return code 0x420E0085 (Multihop configuration check failed. Please remove multihop commands before proceeding to downgrade). This failure is expected as there is an active BFD Multihop session; however it is not possible to remove the default MultiHop configuration as suggested in the pre-check output.

Conditions

BFD feature is enabled. All Nexus platforms supporting BFD Multihop. Have an active BFD Multihop session(s). This is seen running 9.2(X) & 9.3(X).

Workaround

A - Shutdown active BFD Multihop session(s) identified through `show bfd ipv4 neighbors multihop` or `show bfd ipv6 neighbors multihop` B - Disable the BFD feature then reenable it after the downgrade has completed

Further Problem Description