Some US based cellular networks require a lower than default MTU to be used on our router's PPP interface.
If the MTU is left as the default value, the result will be that packets larger than the network maximum will be discarded. This shows up as web pages not displaying in the web browser when using our cellular router as a gateway to the internet.
Recommended values are:
AT&T 1420 bytes
Verizon 1428 bytes
Others 1430 bytes(PPP interface default is 1500 bytes)
To ensure our routers work well on all carriers. set the PPP interface local and remote MRU to 1420.
Via CLI (telnet / SSH / 'Execute a command' in the GUI):ppp 1 l_mru 1400
ppp 1 r_mru 1400
config 0 save
ppp 1 deact_rqBG 21/4/174
Feb 27, 2019