Change IP of WRT1900ACS to configure IP Passthrough?

Just had AT&T Fiber installed and it comes with Arris BGW210-700 modem/router gateway which must be used, does not have bridge mode, closest thing being IP Passthrough, or so I have read.

I have found several "guides" online on how to setup the IP Passthrough ( I still have questions and would also appreciate any help if I show any misunderstanding in the following:

  • put Arris in IP Passthrough mode

  • select DHCPS-fixed

  • manually enter the MAC address of the Linksys WRT1900ACS (which is currently running openwrt) into the "Manual Entry" box

  • connect Arris and Linksys together. LAN port on the Arris, WAN (internet?) port on the Linksys.


i) Besides typing the MAC address of the Linksys in the "Manual Entry", do I also need to select the Linksys from the device list? There's no mention of that in the above instructions

ii) I have read in other "guides" that the Arris and the router behind (in this case the WRT1900ACS running openwrt) cannot use the same IP range. Arris gateway is at (so does that mean it uses 192.168.1.X range?) and the WRT1900ACS uses (so does that mean it also uses 192.168.1.X range?). If so, then I need to change the IP range of the WRT1900ACS correct? How?


At least as I read those instructions, it seems as though what might be happening is that the modem is "passing on" the DHCP it receives from AT&T to the router, changing the MAC address (and perhaps a couple other things) so that the router picks up the assigned IP address and routing information. Sort of ugly, but it seems as though your router will get a public IP address as a result.

Based on my experiences with Arris and Motorola modems, I would assign a non-conflicting LAN subnet, even if not "technically" required. This would let you assign an IP address on the modem's management interface's subnet that you could SSH forward to access from a LAN-attached desktop.