Bridge mode physical connections

Question

I've seen several posts about setting up the SF XG in L2 transparent bridge including the official artical below. I have a Comcast modem, a Ubiquiti Edgerouter X and a LAN switch that I'd like to incorporate this into. My question is, what does the physical connections look like in terms of the LAN/WAN ports on the SF. Do I connect the SF LAN port to my switch and the WAN port to the ERX as the only connection to it? Or do I connect both LAN/WAN ports to the ERX? 
 community.sophos.com/.../122973

Devon Harding · Accepted Answer

The more I think about, that's what I'll end up doing and pulling the Edgerouter entirely. 
 I originally wanted to add the XG for the purpose of web filtering for my kids (hence the reason I went bridge mode) 
 Then I noticed that that dashboard started to show false attacks from Google DNS (8.8.8.8) which may be caused by the bridge mode setup. I also noticed that my Ubiquiti UNMS application was not connecting. It turns out that I now have to manage two sets of port forwarding, ERX & XG. 
 
 I'm going to reset the XG to defaults and build as my primary gateway. We'll see how it goes. 
 Thanks all.

john_kenny · Answer

I would suggest trying with a fresh XG setup as you say, but this time choose Gateway mode rather than Bridge mode, then all you would do is connect your WAN interface from your XG box to your Modem and enter your ISP PPPOE/A credentials if needed. Then your Switch moves to the LAN Int of XG, XG will then be your main DHCP server just dont forget to remove DHCP from any other device on your LAN.