Add-NetLbfoTeamMember : Validation failed and changes to the system are rolled back.

Had a situation where a NIC in a Dell Server would only negotiate 100Mbps. Turns out it was a dodgy network cable, but in the process I reapplied the Broadcom firmware on the NIC.

I had removed the NICfrom the LBFO team as part of the troubleshooting. After we found it was the cable I needed to add the NIC back to the NIC team.

When I tried I kept getting this error below:

Turns out that the firmware reflash had reset all the NIC advanced settings. Including the Jumbo frame configuration.

Set-NetAdapterAdvancedProperty -Name NIC1 -RegistryKeyword “*JumboPacket” -Registryvalue 9000

After I reconfigured the Jumbo Frame on the NIC it worked!