lte520 modem/router no internet with bridge mode

Bridge mode is twitchy because the modem/router normally does protocol as well as transceiving.  In bridge mode, the router/firewall must be configured to do protocol; as you've discovered, just plugging the router/firewall into the modem/router won't work.  The problem is very likely to be a subtle misconfiguration in the router/firewall - for example, AT&T uses a protocol variation in their ADSL modems which sets a nonstandard subchannel number.

In this situation I would use the modem/router in native mode and plug it into the router/firewall on the WAN port, using the factory default settings as you've described. The effect will be the same and there will be no performance penalty.  Bridge mode is for unusual cases and it doesn't sound like that applies in this case.

Also changed to a better modem/router because looking at 3rd party app that would allow field personnel access back to DB on internal network server.  GOTW3 doesn't sell static IP, since public IP can change, using Dyn Updater to keep up with changing public IP.  Dyn Updater won't work with a double NAT.  That is why trying to use bridge mode.  Cellular ISP do have odd settings and this is probably a needle in a haystack.  I'll work on the settings this weekend when I'm not disputing work flow of business.  Unless you have any further info, and/or my efforts this weekend don't fix the issue, we will no longer pursue 3rd party app project.

Many routers have the capability of doing dynamic DNS internally.  Here is an example - a WNR2000 which is by no means a fancy router.  You might try putting your dynamic DNS on the router instead of inside the LAN.


I would note that my own server is inside a double firewalled LAN with two separate address translations and the dynamic DNS works properly.  ddclient is capable of dealing with these things when properly configured.

I was able to look at manual for LTE520 modem/router and it does show a DDNS tab, so I'll give that a shot.  I've been setting the T55 up with DDNS.