Your ISP's DHCP is not functioning properly - Xfinity

BGood

Occasional Visitor
Since mid-week, I've gotten the message "Your ISP's DHCP is not functioning properly" with my Xfinity Gateway in bridge mode. Exiting bridge mode (double NAT) works fine. I tried swapping to a new Arris SBV3202 modem with the same result. I found similar messages and I've done lots of suggested things. I had this problem a year or two ago and I was able to change my DHCP to "continuous" from "aggressive" and that worked well for a long time. This time it did not.

So I finally did the hard factory reset (holding WPS button while powering on), and the darn thing got an IP address and worked. But I have a lot of settings, so I restored my last CFG backup and went right back to borked.

Merlin 386_1_2

So it looks like I have to redo everything, but does this mean a hand-jam of everything I've ever done? Can I safely back up the LAN DHCP reservations somehow? VPN server? Anything else? What tools are available to do that?

Would now be a good time to install the Merlin 386.3_2?

Sorry to ask for a bit of hand-holding, but I'm coincidentally dealing with a health issue right now and I just don't have the strength and energy to dive into good research to make this right. I'd appreciate some guidance, please.

Thank you all.
 

Tom Ames

Regular Contributor
I'm not the best informed to help you, but I got the same message from Xfinity a few days ago. I'm on the current alpha firmware. After some poking around on Xfinity's site, it seems the only way to do what they wanted was to change my modem from bridge mode to router mode. Obviously I was unwilling to do that, so I ignored their warnings. I have not received any further notice from them.

Not sure if related to the above, but they are replacing my current modem with a new model soon. In fact, it is already in transit to me. Not sure about your situation, but I decided that the best course for me at the moment is to do nothing--other than replace the modem when it arrives.
 

Wisiwyg

Senior Member
Try WAN settings, bottom of page, DHCP frequency, set it to Aggressive. Works for me on Xfinity.
 

BGood

Occasional Visitor
This is the only guaranteed solution. What's your issue in double NAT?
Hard resetting the modem to defaults resulted in a DHCP IP right away. Why wouldn't I want to do that?

At a minimum I'd need to do some port forwarding to get Openvpn to work. There's at least one other issue that I can't recall right now.
 

BGood

Occasional Visitor
All "issues" in double NAT have a relatively easy solution. Place your router's IP in DMZ to avoid port forwarding on 2x devices.
That will only work if I forego using the Arris cable modem, which is not a router, and continue to rent for $14/month.

So you're saying I'm wasting my time starting over with the Asus router because it will break again at some point?
 

Tech9

Part of the Furniture
So you're saying I'm wasting my time starting over with the Asus router because it will break again at some point?

You're not the only one with this issue:

What I'm saying is you can fix your WAN disconnection issue permanently, similar to this:
 

SomeWhereOverTheRainBow

Part of the Furniture
Since mid-week, I've gotten the message "Your ISP's DHCP is not functioning properly" with my Xfinity Gateway in bridge mode. Exiting bridge mode (double NAT) works fine. I tried swapping to a new Arris SBV3202 modem with the same result. I found similar messages and I've done lots of suggested things. I had this problem a year or two ago and I was able to change my DHCP to "continuous" from "aggressive" and that worked well for a long time. This time it did not.

So I finally did the hard factory reset (holding WPS button while powering on), and the darn thing got an IP address and worked. But I have a lot of settings, so I restored my last CFG backup and went right back to borked.

Merlin 386_1_2

So it looks like I have to redo everything, but does this mean a hand-jam of everything I've ever done? Can I safely back up the LAN DHCP reservations somehow? VPN server? Anything else? What tools are available to do that?

Would now be a good time to install the Merlin 386.3_2?

Sorry to ask for a bit of hand-holding, but I'm coincidentally dealing with a health issue right now and I just don't have the strength and energy to dive into good research to make this right. I'd appreciate some guidance, please.

Thank you all.
This is a common occurrence with asus routers and cable modems in that some cable modems do not adequately connect properly with the cable modem service provider. it really boils down to looking at what type of errors are in the modems "log". (not the routers). Ip of the cable modem is usually something like 192.168.100.1 for example. I have had this error before, what resolved it for me was switching the WAN ISP special requirements "DHCP query frequency" from Aggressive to Continuous. It varies from ISP to type of modem used and errors present on the modems Log.
1635746152497.png

One thing i would definitely try doing is to have your ISP reprovision the modem you are using. It could be in part caused by a glitch on their end.
 
Last edited:

JWoo

Senior Member
The Motorola MB7621 cable modem works well with Xfinity Internet (and is approved by Comcast) and only costs $80 - $90 depending on where you buy it. After 7 months, the cable modem has paid for itself by getting rid of rental fees from the ISP. The Motorola MB7621 also works well with about any router, including those with AsusWRT Merlin. Arris cable modems also get VERY VERY hot in operation and the Motorola MB7621 runs pretty cool. I have never gotten much more than a year out of any Arris cable modem due to their heat issues.
 

Paliv

Senior Member
I actually found Normal Mode for DHCP query helped for me. Aggressive or continuous seemed to query the ISP device too many times before it would hand out an IP and the light would go red. I also have to time the turning on of devices just right. Too soon and the ASUS queries too early, too late and the Comcast box just seems to refuse to talk. Normal mode seemed to help me get into the right window better. The only problems I have is when I lose power.
 

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