Possible MTU problems with Verizon 4G LTE jetpack tethered to USB modem

Installing and Using OpenWrt Network and Wireless Configuration
1

I have a Verizon Wireless Novatel 7730L hotspot tethered by USB to a GL-AR300M router with OpenWRT 18.06.0-rc1 r7090-d2aa3a1b62 installed.

I'm using the hotpost as my internet source, and it is working; however, website loading has been inconsistent. Sometimes sites will load fast and work fine, and other times sites will load slowly, partially, or not even load at all. All the while, pings to google.com are very consistent.

In reading up on this, I'm suspecting this might be an MTU issue, although I admittedly don't know a lot about this. So I want to make sure all of my MTU / MSS clamping settings are correct and are applied to the correct interfaces.

In OpenWRT, I have changed the MTU for both the LAN and the Tethering interfaces to 1428. I have also enabled MSS clamping on both the LAN and WAN firewall zones.

I have used the mturoute.exe tool (found on another forum) to do tests to both Google and to my gateway. The result for Google says the path MTU is 1428, and for my gateway it says the path MTU is 1500.

Does this all sound correct? Is there anything else to consider or to check? For instance, do I need to change the MTU on my computer's network adapter?

Would appreciate the help in getting to the bottom of this!

2

I don't think it is an MTU or MSS issue. If it was MTU to blame the same site wouldn't load at all. But you have different results, that point to bad connection. Moreover if you don't understand what these things do, it could make it worse by messing with them.

First remove any MTU or MSS setting on the LAN interface.
Second check for the optimal MTU and cross check it with Verizon.
Third don't mess with the settings on your PC.