LB2120 constantly failing over even though wireline is fine

TimeFramed · ‎2020-06-08

I've hade an LB2120 for a while now without issues. But lately, it is constantly failing over to the mobile broadband for no (apparent) good reason. The wireline (cable modem) is up and running at the time.

I tried adding (the max?) addresses to the ping configuration in the hopes it was transient issues with pinging a particular site. The list now includes:

8.8.4.4

8.8.8.8

(btw, there seems to be no way to control the order...)

Adding the additional ping addresses did not seem to have any affect at solving the problem.

I refuse to believe that all 10 addresses are failing to ping, consistently enough to cause a failover (and prevent returning to wireline).

Maybe DNS servers are being hammered lately? If both 8.8.4.4 and 8.8.8.8 become unresponsive, I suppose all of the others would fail due to the inability of resolving the names. Maybe I need to put some more hard-coded (numeric) IPs?

Currently, I've disabled failover, and things are working fine, because of course the wireline connection is fine.

My primary purpose for the modem is that I automatically turn off the cable modem at night so that the overnight streaming (people falling asleep) is done on my unlimited wireless data plan, and not my limited (grr) wireline. That works fine, and switches back to wireline in the morning when the cable modem is turned back on.

It's extremely annoying, though, when it fails over to mobile unnecessarily, because (a) it's slower than cable, and (b), not everything is resilient to that switch; in particular things that don't like that your IP address has changed (e.g., Elite Dangerous will dissconnnect you, and requires a re-launch on the new IP).

The LB2120 is set up in "router" mode with an Orbi on the LAN end. Bridge mode does not work; presumably because the orbi isn't particularly happy with the WAN end changing either (or at least requires a reboot or long wait for it to request a new IP); in router mode, presumably, the LB2120 determines the IP for the Orbi, which remains valid after failover, and return to wireline.

Of course, once the LB2120 is in failover mode, claiming that wireline is unavailable, there is no way for me to manually ping those addresses on the wireline (the LB2120 manager interface should allow some sort of exposure in this area... show the ping information that lead to the failover, and the current ping status information -- i.e., why it's not returning to wireline).