Why does tunnel-node mtu on controller does not take effect with UBT/PBT?
Aruba controller has the capability to act as MUX client and terminate the GRE tunnel on a different controller.
Aruba Switches can form GRE tunnel with controller with either of the two ways:
UBT - User-based Tunneling
PBT - Port-based Tunneling
With UBT/PBT, the controller acts as a MUX server.
The command - tunnel-node mtu is applicable on the controller only if the controller acts a MUX client and terminate the tunnel on a different controller.
In the cases of UBT or PBT, where the controller acts as a MUX server, the MTU value for the tunnel has to be configured on the MUX client (Aruba switch) and the tunnel-node mtu command on the controller will have no effect with the tunnel formed for UBT/PBT.