WAN router upstream from Firewalla Purple

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Dan Porath

• March 14, 2026 12:08

I currently have a firewalla purple and have a spectrum broadband ISP connection I also have a T-MOBILE 5G gateau as my backup. I can't use WAN FAILOVER via WiFi because the T-Mobile gateway creates a double nat and cause havoc whenever it fails over, so I end up having to unplug spectrum and plug in T-MOBILE to the firewall WAN Ethernet port for it to work. Which defeats the purpose. Can. I put a TP-Link ER605 V2 Wired Gigabit VPN Router and let it deal with the dual Ethernet ISP connections and just connect a single port from the vpn router? Essentially letting the vpn router handle my wan connection load balancing and failover?

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  Firewalla

  • March 14, 2026 21:33

  "I can't use WAN FAILOVER via WiFi because the T-Mobile gateway creates a double nat and cause havoc whenever it fails over, "

  What kind problems are you getting? double NAT should NOT cause any issues when failover happens. A few of us use T-Mobile as a failover, pretty sold. 

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  Dan Porath

  • March 14, 2026 22:05

  My deco wifi APs never connect. I guess I don't recall if my hard wired devices connect but it's not been a great experience. It fails over fine. But wifi and device access after it fails over never seems to work on T-Mobile wan via WiFi. However if I remove the spectrum wan cable from the firewalla purple wan port and plug a cable from the T-Mobile gateway lan to the wan on the firewalla it works as expected without issues.

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  Firewalla

  • March 14, 2026 23:12

  Are you using the Firwealla Purple's WiFi connecting to your T-Mobile WiFi? if you are, see if you can disable T-Mobile from using DFS channels on the WiFi side. Or use 2.4Ghz only channel. 

  I suspect your backup WAN via WiFi to T-Moile may not be fully up. Try 2.4ghz will gurantee there is DFS issues

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  Dan Porath

  • March 15, 2026 18:18

  There are virtually no options for disabling or enabling any stations on the gateway. Bought the TP-Link Er605 for 50 bucks yesterday solely to deal with the WAN load balancing and failover. I got it all setup this morning and only dropped about 4 or 5 pings when I pulled either the spectrum or T-Mobile cables from the new router. That's plenty good enough for the girls I go out with. Thanks for the responses and thoughts.

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