Gateway Monitor + Xfinity

ptyork

I've got an issue with using a new Xfinity service in a Multi WAN setup. Specifically, although I can initially get it running with monitoring, it will eventually move to 100% packet loss (maybe a minute or two). No problem whatsoever with the other ISP. Hoping someone can help me to diagnose and fix the problem.

I'm using Xfinity's newest modem/router. I'm trying to run it in Bridge mode (bypassing the built-in router and disabling the WiFi radio). The problem seems not to surface if running in the default router mode (yes, I'm monitoring a downstream IP, not the router's local 10.0.0.1).

I've tried to use the default monitoring IP and numerous other downstream IP's (3 different public DNS providers). I've tried completely dropping the gateway and interface and recreating it. I suspected it may have something to do with changing to and from bridge mode so kept it constant while completely recreating the interface, gateway, gateway group, DNS, etc. from scratch. All eventually result in the monitor reporting the gateway as down due to packet loss.

I suspect one of two things (meaning it's probably a third).

Xfinity is blocking repeated ICMP packets as potential DoS unless routed through their router. (seems pretty unlikely)
Something odd is happening with the static routing rules that get created automatically by the gateway monitoring service. This is supported by the fact that if I disable monitoring, I CAN ping the monitoring IP's no problem.

Any ideas? It's happily running if I accept the few milliseconds of delay, extra power draw, and extra Wi-Fi RF interference of having the modem in router mode. But I don't want to accept that....

ptyork

Just closing this one out. The answer to this was posted here: https://forum.netgate.com/topic/171690/comcast-bridge-mode-sudden-packet-dropping-dhcp-release-renew-solves-it