An engineer must repurpose a lab WLC appliance for use in the production environment of the enterprise. After the new WLC is configured with the information of the other WLC, the mobility tunnels are

While UDP ports 16666 and 16667 are used for mobility traffic, a firewall blocking these ports would not be introduced solely by reconfiguring a controller's identity, making it an unlikely root cause in this specific scenario.

Management interfaces being on the same VLAN can introduce routing issues in some topologies but is not a direct or typical cause of mobility tunnel failure between controllers.

Cisco WLC mobility functionality is not restricted by hardware platform differences as long as compatible software versions are running, so hardware incompatibility is not the reason the tunnels fail.

For a mobility tunnel to come up between two Cisco WLCs, both controllers must be configured with the same mobility group name or must have each other explicitly added to their mobility peer lists. A lab WLC repurposed for production likely retains a different mobility group name than the existing production WLC, which prevents tunnel negotiation from completing. Aligning the mobility group name on both controllers resolves the issue.