DHCP requests are passing through the WAN interface of Google wifi to my upstream ATT router

[wasserdgy]

How can I prevent DHCP requests from passing through the WAN interface of Google wifi? I have followed ATT's instructions at https://forums.att.com/conversations/att-fiber-equipment/ip-passthrough-options-more-details-please/... to put their router in IP passthrough mode successfully- the Home app shows my google wifi router WAN interface has my internet connection's public IP address info, but clients connected to the LAN interface sometimes pull a DHCP address from the ATT router- I can tell because I use a different subnet on the ATT LAN interface DHCP settings. Nothing is connected to the LAN side of the ATT router except the Google wifi router, and ATT router's wifi is disabled.

[olavrb]

You've not configured your Google Wifi to be in bridge mode? And you've bridged the modem, things like NAT and DHCP is for sure disabled? Maybe you've set static IP on the devices that get an address outside the Google Wifi subnet range?

[wasserdgy]

Oh this would be so much easier if ONLY it was possible to put these ATT routers in bridge mode, unfortunately this is not an option. They have ip passthrough as an alternative, but only using DHCP on the ATT router actually allows the Google wifi WAN interface to obtain the public IP of the ATT circuit. For now I have limited the ATT router DHCP server range to a single IP address and disconnected all devices from the LAN when I boot up Google wifi, insuring it gets that address. Not ideal in the event of power outages etc, but is a workaround.

I am assuming this issue of DHCP requests allowing to be passed through the WAN interface has something to do with the "idiot proofing" Google has done to make setup incredibly easy, as I have seen user reports that it seems some people have inadvertently reversed their WAN and LAN Ethernet connection and the Google wifi still functions properly.

[Jeff]

Hi, wasserdgy.

It looks like you and olavrb had sorted out what's going on here, but I wanted to follow up to see if there's anything else I could do for you. Just as an aside, have you been able to speak with your ISP to see if they do offer routers that would allow you to run in bridge mode? It might be worth reaching out.

Anyway, if there's anything else I can do, please let me know. Thanks!

[Jeff]

Hi, everyone.

As we haven't had any activity here recently I'm going to go ahead and close the thread. If you have more to add, feel free to start a new discussion.

Thanks