OpenWRT (and friends), no WAN DHCP

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WonderWoofy's picture
OpenWRT (and friends), no WAN DHCP

Hello all, I just created an account, and have been perusing things around here. Nice place you got. :)


So I have noticed that with OpenWRT Attitude Adjustment, and its descendents, I cannot get a WAN DHCP lease.  That is, the connection between my cable modem and OpenWRT/DD-WRT/CeroWRT/Gargoyle routers will not initiate.


This doesn't seem to be an issue with the early Backfire or earlier releases, though I tried a couple of the later Backfires, and they did the same thing.


This occurs on both my WNDR3700v1 as well as my WNDR3800.  So at the moment I have put an old Linksys/Cisco WRT160Nv3 in between the cable modem and the primary router/LAN DHCP.  This is working perfectly fine, and I have even set it up so that the Linksys provides a DHCP lease to the WNDR3*00 routers.


So I cannot for the life of me seem to figure out why it can find a DHCP lease from another router, no problem.  But when I put up to the cable modem, it craps itself a cries a little.


BTW, my cable modem is a (seemingly) new Arris TM722G Telephony DOCSIS 3.0 Cable Modem.  It runs on, and typically feeds an address in the mid-250s to a router that works with it.  I cannot get very deep into it though because it is a Comcast device and it pretty locked down.


Is there anyone out there that has faced similar issues?  Is this something I should take up with Comcast?

WonderWoofy's picture
I am not one to "bump" a

I am not one to "bump" a thread usually. But I still have not resolved this problem. I have tried all forms of OpenWRT, DD-WRT, Gargoyle, etc. But the it will only pick up a DHCP lease if I go back to firmware from somewhere around late 2010 or early 2011. So it is not specific to any one form of the firmware. As it seems to be inherent within OpenWRT and continues down the forks.

For now I have just set up an older Linksys router in between my WNDR3700 and my Arris TM722G cable modem. The in-between router only has fast ethernet (100Mb/s), but I figure that is fine since my internets are only 50Mb/s. Though we do seem to incur a half ms penalty for that one additional piece of hardware in the middle. Oh well.

If anyone has any idea, I'm totally open to ideas (and willing to tinker with software). ATM, I have Gargoyle on there, since it is a nice simple interface (for my family) and also retains the opkg package management system. It is very nice and easy enough for my family to get a grasp of.

Phil48317's picture
I tried the same thing and

I tried the same thing and for some reason OpenWRT wiped out my Mac addresses. You may want to check that. I ended up going back to dd-wrt (mac addresses still missing) and manually set my mac address to the one listed on the sticker attached to the router.

WonderWoofy's picture
Thanks for the answer Phil.

Thanks for the answer Phil.

The sticker on the bottom of the router is the LAN mac address (at least on netgear routers). The WAN mac address is just bumped up one from the LAN on Netgear routers, so I checked my WAN and LAN mac addresses. Unfortunately they are correct... or I guess maybe fortunately, depending on how you look at it.

I had seen a OpenWRT bug report for this when I was putzing with this, and checked them out then as well. But if that were this were the case I think I would probably not be picking up a WAN DHCP lease from the alternate router either.

j295's picture
I had the same problem. See

I had the same problem. See my bug report and proposed fix at

WonderWoofy's picture
@j295, you are a bada$$.

@j295, you are a bada$$. Unfortunately, I am not home right now to test this out, but you can be absolutely f*ing sure that I am going to test this out as soon as I get back home on Monday. Your proposed fix makes total sense, and I am excited to give this a whirl. It actually looks as though this change has already been committed to the latest builds.

I have been waiting for an answer, and was actually losing hope on this forum. For now I actually have an old Cisco router set up between the cable modem and my WNDR3700... not an idea solution, but it worked for the time being.

Cirrusflyer's picture
I'm seeing the exact same

I'm seeing the exact same thing on 2 different WNDR3700v1 routers, both with latest version of Gargoyle. And I'm on Verizon FIOS. And I also implemented j295's patch, but with no luck.