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Comcast DHCP issues with some Asus routers?

andyross

New Around Here
There are several posts in the Comcast forums about users having problems with their Asus routers and Comcast. It will not connect and gives a message that the DHCP is not functioning properly. Some have it fixed by getting the modem properly provisioned, but that doesn't always work.
Has anyone seen this? Any ideas on what is going on? I have a 68U that is working for now, but I'm holding off on any firmware updates, just in case.
 

ColinTaylor

Part of the Furniture
I have a 68U that is working for now, but I'm holding off on any firmware updates, just in case.
Download a copy of your current firmware from the Asus website then backup your current configuration (Administration > Restore/Save/Upload Setting > Save setting). If you have problems after updating the firmware you can always go back to this previous known working setup.
 

dancinjammin

New Around Here
Here is my experience and my work around for now.

I have been through this a few times with Comcast/Xfinity.
My current configuration is all ASUS routers in Aimesh behind the Xfinity Cable Modem/Router. I don't believe this is an Asus issue. I tested with a Netgear R7000 and an old linksys and had the same issue.
So, unless either party will fess up to a known issue (which to my knowledge they have not), here is my quick fix.

The flaw, as I see it is in the Comcast/Xfinity bridge mode implementation and how it works what the Comcast DHCP servers.

Stick a pin in the Comcast/Xfinity cable modem/router to reset it (to default router mode) and only plug your laptop into a port on the Comcast/Xfinity cable modem/router.
Default router IP should be 10.0.0.1 with login of "admin" and "password" for the password.
Then toggle the bridge mode on and plug your Asus router back in. It should take about 20 minutes to get you back in business. That way you won't waste 2 hours on the phone with Comcast.
I have to do this about 4 to 5 times a year.

I ran my Xfinity XB6 (Arris TG3842G) as a router for a couple months with out issue. But the XB6 does not have the router features I want.
So I run the XB6 in bridge mode and use the VPN and other features on my ASUS router. If the flaw is proven to be up in the Comcast DHCP servers, I may request to see if I can get a semi-permanent IP address and try to get around the DHCP issues.

Please let me know if this helps.
 

andyross

New Around Here
I have my own modem, which I've had on Comcast for several years (Zoom 5341J). Users have reported issues with stand-alone modems, not Comcast gateways in bridge mode.
 

bluzfanmr1

Regular Contributor
I suggest doing as I did. Comcast has an approved list of hardware and they will allow you to use your own modem. At $13 per month to rent their modem, it won't take long to recoup the cost of buying your own. I found a slightly used Arris Surfboard cable modem for about $25 and have never had an issue.
 

bbunge

Very Senior Member
Comcast commercial account but have static IPV4 addresses. Have not gotten IPV6 to work reliably even after Comcast upgraded the modem router which is in bridge mode. Using AC68U Asus.
 

Lee MacMillan

Occasional Visitor
There are several posts in the Comcast forums about users having problems with their Asus routers and Comcast. It will not connect and gives a message that the DHCP is not functioning properly.
I've been using my 66U-B1 with an Arris SB-6183 for over 2 years. I keep the firmware up to date. Never had an issue. I have 2 wired connections and sometimes as many as 12 wireless connections.
 

andyross

New Around Here
I did update the firmware over the weekend. No issues.

I still wonder why Asus seems to be the only one with issues? Is there a bug in it's ISP DHCP routines? Or is it just pickier about something?
 

EmeraldDeer

Very Senior Member
My take is that "WAN_Connection: ISP's DHCP did not function properly." is a catch all error on Asus routers for any WAN outage. The cause could be anything.

When Comcast could not handle the extra load a few months back of everyone working from home and online schooling, I received this error. Normally I never see this error.
 

sol1109

Regular Contributor
I have had 68U since 2013 behind a Comcast VOIP modem without seeing this error. I recently dumped the landline and rented modem buying an approved Netgear CM600 and have had no problem. In fact, my speed testing has seen a 240% download improvement since replacing the Comcast device.
 

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