GRE tunnel also supports IP Maximum Transmission Unit (MTU) configuration. When the IP packet size exceeds the configured IP MTU value on a tunnel, the Path MTU (PMTU) mechanism can be used to notify the sender of the traffic that the packet size needs to be reduced.
Use the configure tunnel tunnel_name ip mtu mtu command to set the MTU value. The default is 1476.
This feature is only available on ExtremeSwitching X590, X695, and X465 series switches.