I switched my asterisk system from a sonic.net static IP to a Comcast Business cable modem with dynamic ip. I thought my system was running ok (I could dial out etc.), but then someone told me they couldn’t dial in.
After a lot of futzing about, I found that asterisk/freepbx doesn’t work well with with double NAT (i.e. cable modem with NAT + tomato router), but in a non-obvious way. You can dial in to the IVR, but all of the internal phones are always busy.
It’s not easy to get the cable modem to bridge. Comcast wants $14.95/mo for static IP, which I find outrageous and refuse to pay. I tried (a) turning off the firewall in the Comcast modem (SMCD3G-CCR) and (b) put my tomato router in the DMZ of the cable modem. Neither helped.
So, for now, I’ve switched back to sonic.net. Does anyone have any suggestions as to how to get asterisk to work with Comcast? (or a least a more detailed explanation of why DMZ and/or no firewall doesn’t help…)
There is some hope that the Motorola SB6121 cable modem allows bridge mode - I’m going to try that next.