Mar 30
Comcast Blocking DD-WRT?
About a month ago, I received a notice in the mail from my ISP, Insight, with news that they had been bought-out by Comcast. They promised that there would be no changes in my service and the transition would be seemless. Everything would work as it had, except they would charge a little bit more. Great.
They’re in the midst of transferring services to Comcast, set to be complete sometime in April. Everything was fine on our end until our internet went out a few days ago. After a few hours of toying with it, I decided it had to be Comcast’s issue. I tried rebooting the router, renewing the IP, and even connecting my computer directly to the modem– nothing worked.
Finally, I called Comcast and talked to one of their “specialists” from Indiana (better than India, right?). He dialed into the modem, and was able to get a computer hooked up through the modem, but still not through the router. We made an appointment to have somebody come out.
Two days later, somebody from Comcast came out and tinkered with things for about an hour. With all of the toys in his magic bag, he still couldn’t get the router working. Moreover, we were able to hook up a different router, and that one worked. We chalked it up as a faulty router, and he was on his way. But something was still fishy.
We bought the router about 5 months ago, and everything had been working on it perfectly. I installed the DD-WRT firmwire for even more control. Everything looked good on it, except we couldn’t get an IP from the modem. After doing a little research, it seems that Comcast has some trouble with DD-WRT routers. The solution was to change the router’s MAC address from the default DD-WRT address to something else. Many users clone their laptop’s MAC, but I used one from an older router. A quick reboot afterwards, and we’re back up.
It’s hard to say whether it’s an incompatibility issue, or Comcast is actively blocking this alternative firmware. I’ve generally had bad experiences with Comcast, so I choose to believe the latter. Anyway, I’m glad we got things worked out, because I wasn’t too excited about going through the warranty process with Linksys either.
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April 5th, 2008 at 9:03 pm
They are probably looking for the MAC address of the client machine. If DD-WRT has the same MAC set every time someone installs DD-WRT there system may get confused if someone else is using it already.. Just speculation.
April 6th, 2008 at 6:46 am
I agree, this is probably the case. But the fact that it essentially disables DD-WRT router, the net-effect is equal to Comcast blocking it. Moreover, the technician had no experience with the problem, and had me convinced that my router had just gone bad. The fact that it should’ve “just worked”, and it has “just worked” for other ISPs, makes it a Comcast problem.
April 21st, 2008 at 3:29 pm
Interesting in that I had simular experience, Put DD-WRT on a spare
wrt54g. Swapped it out with my old befsr41. Nothing. waited hours and
cycled power etc. etc. Swapped the befsr41 back and connection was up again.
I believe that Comcast only has the MAC of my modem (my modem got changed
recently, and I watched the tech register the new modem MAC) in their system
but decided to change the MAC on the WRT54g anyway.
As soon as I did that, I had a DHCP lease, same ip as before.
(I used the MAC from the old befsr41)
April 23rd, 2008 at 4:16 pm
This just happened to me today. I put dd-wrt on my router about a month ago and it worked fine until this morning. Interestingly, I couldn’t even get a DHCP lease with my laptop wired directly to the modem until I called tech support.
After we got my laptop working I hung up and hooked the router up again…no DHCP lease. Cloned the laptop MAC address and everything works now.
By the way this page is the #1 Google hit for “comcast mac address blocking” right now.
April 23rd, 2008 at 5:23 pm
Thanks for the comment Chris. It sounds like we’ve really hit something. Is Comcast new in your area by any chance? I wonder if it is location-specific. I am in Urbana, IL.
April 24th, 2008 at 6:36 am
I’m in Sarasota, FL. I’ve lived in the same apartment for three years and have always had Comcast.
April 26th, 2008 at 8:55 am
Thanks for this post. I have Comcast, located in Chicago (Wrigleyville), and about a few weeks ago I started having issues with my router. I’ve had DD-WRT installed for almost a year now with no issues, but all of the sudden I had no connectivity, and could not figure out the issue at all. F#%@ comcast
July 14th, 2008 at 1:14 pm
I’m an IT professional and run a side biz servicing home users as well as small business in my area. Over the last week I have had 2 clients (both Comcast) contact me with the exact issue verbatim. One lcient uses a Linksys router the other Netgear (both manufacturer firmware). The solution was to clone their PC mac addresses in their routers.
When I signed up for Comcast over a year ago (and dropped Pay-T&T) I already had a Linksys router with Linksys firmware. I had to clone the PC mac address I used to set up my Comcast service to get my router to work. Later on I installed DD-WRT and still had to clone my Mac address. So the mac address cloning issue is not DD-WRT related at all as I had to clone it pre-DD-WRT and both of my clients recently (non DD-WRt) all of a sudden had to clone their MAC addresses.
Looking at the dates of the first posts here this leads me to believe Comcast is slowly but surely setting all their nodes to require the specific mac addresses of the PCs that users activated their service on. I’m guessing this is to exploit money from people making them believe they have to pay an extra $10-20 for Comcast’s home networking plan.
September 26th, 2008 at 3:05 pm
Comcast suddenly quit working with my dd-wrt router after it had been operational for nearly a year. No amount of changing MAC, cloning, etc. worked. Could still get a lease with any old computer – but not with dd-wrt, no matter what. Finally ended up putting stock linksys firmware back in place, which worked.
October 17th, 2008 at 7:11 am
Update: One month after putting the stock linksys firmware back in place, the router can no longer get a DHCP lease. Plug in the computer directly — get a lease. Clone the MAC, plug the router into the modem — no lease.
October 19th, 2008 at 2:25 pm
Update: Comcast is blocking uDHCP request packets based on packet length. The only solution I found was to use the tomato firmware on the Linksys router, and check the “short DHCP packet” option. Comcast now grants leases to the router.
December 24th, 2008 at 10:52 am
Communistcast is indeed requiring the MAC address of the interface the service was first registered with. This appears to have started sometime around mid 2008. My only guess is that Day D. above is correct about the attempt to suck extra $$ out of people. And for the record, I have been a network engineer for the past 10 years.
December 24th, 2008 at 4:01 pm
I had the same problem today. I have a Linksys WRT54GS, and all of the sudden it stopped working. I just did the MAC Address Clone (from the original PC to the router) and it seems to be working again…for now. Thanks for the info.
December 24th, 2008 at 4:11 pm
I also have a Motorola Surfboard modem. Someone had suggested a hard reboot of that might have helped too. Haven’t tried it, since the MAC Address Clone worked. Just an FYI.
January 3rd, 2009 at 3:32 pm
[...] Comcast Blocking DD-WRT? [...]
January 30th, 2009 at 11:12 pm
FYI… The cable modems record the MAC address of the first device it sees on the LAN interface. So if you had it connected to your PC, that is why your PC’s MAC cloned on your router will fix the problem.
DD-WRT does not have a fixed software MAC… It will use the MAC address for your hardware.
(Unless you use the clone feature, that is.)
What those crafty twits have done now is what really got me. Power cycling the modem did not reset the MAC address lock-in as previous modems would. You need to follow the “eMTA” reset procedure to reset the MAC address lock-in. They include using a pencil, paperclip, or other pointed object, depress the recessed ‘reset’ button until the lights on the front of the modem turn off. This process reloads the modem’s management data from Crapcast’s server. The process can take up to five minutes.
March 23rd, 2009 at 10:49 am
I’ve been experiencing this problem, however I believe there is something in dd-wrt firmware that does not work with Comcast. I have been using
an old d-link 614+ router for years with Comcast and it started giving me problems so I got a wrt54g and it has been working fine for the last year.
I recently flashed it with the dd-wrt v24 sp1 and it will not recieve a DHCP lease from comcast. It is not a MAC address issue either because I
have been using the router fine with the original firmware and I didn’t have a problem using a my computer directly connected to the cable modem
either. Perhaps it has something to do with the modem forwarding the dhcp requests? It is really frustrating. I hope someone can find a definitive answer to this issue.
March 24th, 2009 at 7:14 am
I recently had my modem replaced after countless yelling at comcast. The original RCA brand modem was replaced with a Motorola modem and my issues are resolved. I had updated to v2.4-sp1 recently from v2.3 and I see vast improvements there also (although that didn’t fix my problem).
April 16th, 2009 at 5:51 pm
I’ve just ran into this problem after calling scumcast about slow upload speeds. They sent out a technician(I’ve seen better demeanors on a raging bull – like I was the slime of the earth.) who after an hour of poking around outside of my house, came in and said it must be my modem. I have to buy a new modem. I got the Motorola Surfboard 5100 he told me works best, and the one he demonstrated worked just fine for him.
I did just that and now after two weeks of crappy connectivity I have lost all access to my internal Zonealarm wireless router. I can only connect directly to the Motorola with one PC.
I called the pleasant people at technical support and explained the issue, to which they started to laugh and said they could send out another technician and bill me the requisite $20, like the last time when they did not fix anything, only made it worse.
If anyone has a clue please give me a hint.
Thanks,
May 24th, 2009 at 9:25 pm
I just came back from vacation to find my comcast service dead, and as others have described I was able to get online with my pc directly connected to the modem, but not with my dd-wrt router in between, even with the PC’s MAC address cloned. What finally got it working was actually resetting the router’s MAC address to its original factory MAC (printed on the label on the bottom).
March 6th, 2010 at 6:53 am
Does my mac adresse change if I upgrade my computer with some other hardware? For example change the graphic card?
March 13th, 2010 at 11:02 am
I recently had the same experience. I installed DD-WRT about six months ago. Everything has been working just fine until yesterday. Like many others have said, plugging directly into the modem (I have Comcast voice, btw) results in internet connectivity.
So I decided to hook up a different router to see what would happen. Still couldn’t get online. It finally dawned on me to try MAC cloning, which seemed to fix my issue. I browsed the web for a bit, closed the laptop and went to bed.
When I went to check my email the next morning, I found that the internet wasn’t working again. So I logged into the router and told it to renew its DHCP info. Still nothing. I decided to plug up the first router (my DD-WRT) and set the MAC cloning on it. It managed to grab an IP and the internet is flowing once more. Which brings me to the present moment. I’m just waiting for my internet to go out again because I still don’t understand why I’m suddenly having so many issues.
Has anyone found an answer/solution?