Specifies that the tunnel maintain information on the maximum allowable packet size (smallest MTU) for the entire routing path of the tunnel. Packets entering the tunnel that are larger than the tunnel’s MTU are either fragmented, or sent back with a request for fragmentation (depending on the DF bit of the packet). Use no tunnel path-mtu-discovery to disable MTU discovery.
Use the age-timer parameter to force the tunnel to update the MTU after a specified number of minutes. Specify infinite to make the MTU value permanent (no updating).
Note:
When MTU discovery is disabled, the tunnel’s source interface marks all packets may be fragmented, even if the packet’s original setting is do not fragment. It is highly recommended to enable the MTU-discovery feature on a tunnel.
