AT&T Remote Access

Has anyone figured out how to remote access a AP1300 or X750v2 on AT&T? Every time I try it times out and fails but I can remote into any AP1300 or X750 I have TMO in.

Might want to be a bit more specific…

ATT Wireless or ATT Internet (internet is the fiber/dsl home/business broadband service)

ATT Wireless. Sorry for the confusion.

Can you do this:

First upgrade to 3.215 snapshot (added mtu setting)
Then set up the modem manuall and use mtu 1428

Did setting the mtu 1428 resolve this issue?
I am having trouble remotely accessing them over cellular with T-Mobile or AT&T

Also try this method (without change mtu)

echo 1 > /proc/sys/net/ipv4/ip_no_pmtu_disc
echo net.ipv4.ip_no_pmtu_disc=1 >> /etc/sysctl.conf