@kenn10 - after all your help yesterday, I was able to get it working today using your last suggestion.
I'm starting to understand why many prefer the cloud servers. BTW, I've used various versions of Tomato since I started messing with Ward's PBX distributions and never had a single problem using any of his PBX's with it, and, it turns out, I
still have not. For the future benefit of anyone else fighting the Arris NVG589 broadband modem: I understand it can't do pure bridge mode or be eliminated from the network because it contains a certificate needed to authenticate the customer to the ISP. Instead of true bridge mode, the device gives a choice of two settings: "PassThrough" and "Default Server". The former assigns the device's WAN IP to router behind it, and passes
*ALMOST* all traffic like a bridge, the latter puts the IP Address of the router into the Arris DMZ. I used "Passthrough" successfully with many projects including Incredible PBX that needed open ports, ever since I owned the Arris modem. Looking at the old call logs, I believe this problem with Anveo began in 2014 when I switched ISP's and began using the Arris. At the time, I simply chose different outbound trunks in FreePBX to defer identifying the issue, never realizing that it was caused, only for Anveo, by the Arris configuration.
I am so so happy to finally have it working! The old Acer Revo running my PBX, with SSD, uses about $28 worth of extra electricity/year where I live and I am very happy to extend the use of it for longer rather than trashing yet another piece of perfectly good hardware.