Your ISP DHCP not working - when modem is in bridge mode - can get an ip when not in bridge

We've seen a number of posts about the same thing here lately. Me thinks that it's a firmware bug.

If you are not, you need to power-cycle the gateway (just like a straight cable modem) after placing it in to bridge mode in order for any connected device to be able to obtain internet connectivity.

thank - yes alreday did that - after putting in bridge mode the gatetway/mode was reset - and it still did not provide an IP for the router

So the weird part is -

1) the router will connect when the gateway/modem is not in bridge mode. - its just that we end up with double nat - and need to turn off the wifi to reduce interference.  performance has not been an issue but we get the intermittent drop between the router and the gateway - just watching it say disconnect / your DHCP msg . . .   now the drops may nothing to do with bridge or not.  And could be something else.

2) tried a different factory reset asus router with the latest firmware from ASUS - and was still getting the same issue - in bridge mode.  No DHCP IP.

3) bridge mode shows no devices connected - though my PC - which was used to set the bridge mode is connected, and can get IP/internet (how am writing on the forum) 

I started having a similar problem to this this past Friday (6/12) or Saturday.  No changes on my ASUS router.  I don't have it set to upgrade automatically or anything.  Still no answer, but what you are discribing sounds similar to what I am experiencing.  

Hi there - I hope I can help out here as I just resolved this for myself.  Took several hours and lots of googling to get it working.  I'll explain the backstory and details, then the solution.

Backstory / setup:

I have had a gigabit xfinity modem (dark grey one) working in bridge mode in front of an Asus RT-AX89X router for quite some time - all worked well with automatic setup - no custom configuration needed.  Today I received the new gigabit xfinity modem (white model capable of 1.2gbps) and set that up in the exact same way.  Long story short - it didn't work.  I was getting the DHCP error on my Asus router.  Here's what I did:

Step 1 - Get the modem working

Connect your PC directly to the modem and get it working.  Use the xfinity app to provision it, etc.  Make sure it all works, run speedtest, etc.  This should be straight forward.  

Step 2 - Power down your ASUS router

Self explanatory

Step 3 - ipconfig release/renew the modem

After the modem is verified working and IS STILL CONNECTED DIRECTLY TO YOUR PC via ethernet, run the following from a command prompt:

ipconfig /release

ipconfig /renew

These commands should run quickly.  After running them, ensure your internet connection is still good - speedtest, youtube, etc.

Step 4 - Bring the ASUS router back in the mix

Plug the cable modem into the WAN port of your router (i.e. remove it from your PC).  Then connect your PC to the Asus router.  

Power the Asus router up.

You will get a solid red light on the WAN port - this is to be expected

You will see the DHCP error on the router page after it boots up.

Step 5 - MAC cloning

Again - Your PC MUST be connected to the router and NOT the modem...  Login to the router configuration from your browser (router.asus.com).  

Under Advanced Settings go to the WAN section

On the 'Internet Connection' tab there is a MAC Address field with a 'MAC Clone' button next to it.

Click the 'MAC Clone' button - this will populate the field with the MAC address of your PC's network card

Hit Apply

Step 6 - The router will soft reboot

The lights will go out and when the come back on, the WAN port will be red for a moment, but then should turn white

Log back into the router - it should now say 'Connected' and the DHCP error should be gone.

SUCCESS!!!

MAC cloning was something that was needed many many years ago with Comcast/Xfinity, but went away.  For whatever reason, it now seems to be necessary again.  

I hope this helps save all of you countless hours of frustration.

Year old dead thread now being closed.