I have an FTTP ethernet connection as a primary to my WatchGuard T80. In the event of line failure I'm trying to setup a DrayTek Vigor 2866Lac to pass through an ADSL line and a 4G LTE connection via inbuilt SIM.

PPPoE pass-through of the ADSL line does not work to the WatchGuard and I can't enable MPoA to setup Bridge mode.

I guess the main question, is the 2866Lac capable of what I need and if yes what do I need to configure to get it there?

Thanks

This is possible (and I have deployed them in this way) but I can’t remember the specifics of what’s needed. IIRC there is a little command line stuff required on the Draytek to allow the MAC ranges used by the WatchGuards. Also check the MTUs.

ip arp accept 5

That might have been specific to my configure, which was an HA pair, hence the VRRP addresses.