Use the following steps to configure MTU on a WAN:
Log into NetCloud Manager.
Log into the router's setup pages. For help with logging in, see Accessing the Setup Pages of a Cradlepoint Router.
Click Configuration > Edit.
Click CONNECTION MANAGER in the left-side navigational pane.
Click the name of the modem within the WAN Interface Profiles & Priority list.
Click Edit.
Set the MTU value based on the testing results in the General tab of the WAN Configuration Rule window.
Click Save.