Peplink Balance 20 with v6.3.2 firmware
WAN1: Motorola Surfboard SB6121, ISP: Comcast
WAN2: Motorola NVG510 in bridge mode, ISP: AT&T
Upon installation of a brand spanking new Peplink Balance 20, WAN1 would generate the error “WAN1 Disconnected (WAN Failed DNS test)” around 10-12 times per day. WAN1 would usually reconnect within 2-10 minutes, but during this time WAN1 would be unavailable. Even when working, DNS resolution was quite slow. The NVG510 on WAN2 worked perfectly.
I tried various fixes recommended on this forum, and elsewhere, with no success including changing the various Health Check options (frequency, timeout period, DNS servers, etc). A Comcast technician came out and verified that the physical line was within specs. Tried connecting the SB6121 to WAN2 and the NVG510 to WAN1: the NVG510 continued to work perfectly on WAN1 and now the SB6121 on WAN2 disconnected. Tried changing the SB6121 power supply, still no change.
Finally, tech support at Peplink suggested that I put an unmanaged switch between the SB6121 and the Peplink to “rule out any hardware compatibility issues”. I used a TP-Link TL-SG105 5 port switch. Since then, the SB6121 has been operating normally with zero disconnections … so it seems like this workaround has solved the issue, although the solution of installing a redundant (and I don’t mean “redundant” in the good way) switch in-line seems pretty inelegant to me.
Any ideas as to the nature of the incompatibility? It seems odd to me that this is even possible nowadays. Can this be fixed via firmware, or is it really a hardware issue? Somehow the SB6121 and Balance 20 do not talk to each other reliably, but the TL-SG105 can talk to both without any problems, I am perplexed.