On our Comcast Cisco DPC3939B modem, we have several public IPs mapped 1-1 to LAN IPs for in-house servers. This worked well for over a year, until the last couple of weeks, when people connecting in from the internet started getting dropped or very slow connections (in one test, a 33 kb file took over 12 minutes to transfer, a rate of about 0.0004 Mbit/sec). Connecting to the servers from the LAN still works fine, connecting to the internet from the LAN is fine, and bandwidth tests like Ookla are fine.
We have not changed anything on the modem or the LAN for months, which leads me to suspect some kind of hardware failure on the modem. We have power-cycled the modem and servers, with no effect.
Is there some way to test NAT on the modem? Cusadmin only seems to be able to test general connectivity. Is it worth resetting and reconfiguring the modem? Any other suggestions before I call support? Thanks!