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Old 12-24-2007, 04:06 AM   #1
Join Date: Jan 2005
Posts: 26
Default Comcast blocking Mac Addresses?

Short version: Does Comcast block Mac Addresses?

Long version: Yesterday, I thought my Comcast High Speed Internet connection went down. I thought at first it was Comcast having issues, but I first tried to rule out a problem on my end. I connected the cable modem directly to my computer (normally, the modem goes straight to a Linksys router), but still no connection. After calling tech support, as a last resort, she suggested I try plugging the modem in directly to another computer. I did, and much to my surprise it worked. She said most likely my router and/or first computer's NIC was bad. It wasn't very plausible to me, but I had no other explanation. I even switched back to the router, just to tell myself that it wasn't Comcast that was glitching and was just all of the sudden working, but I still could not get an internet connection.

Several minutes later, I had a sudden realization. There was something that my router and my NIC had in common. I had the router spoof that NIC's Mac Address. So when I switched the router's spoofing to the second computer's MAC addy, voila, everything was working again.

So again, the only possible explanation I have is that Comcast blocked the original MAC address I was using. So my question is, have Comcast been known to do that, and if so, why?
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Old 12-24-2007, 04:16 PM   #2
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Default Comcast blocking Mac Addresses?

Yes, ISPs can and do block MAC addresses if they think there is a legitimate reason to do so.

What have you been doing recently that is illegal or violates Comcast's terms of service?
"I did RC5, but I didn't flush." - Bill Clinton
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Old 12-25-2007, 01:20 PM   #3
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Default Comcast blocking Mac Addresses?

I know Cox.net will block MAC addresses if there is a known issue with that computer.
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Old 12-26-2007, 05:43 PM   #4
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Default Comcast blocking Mac Addresses?

I haven't had comcast in probaly three years. But I do remember they did block my mac address at least twice. They always gave me no reason as to why, and unblocked it as soon as I called. I figured it out the same way as you. The easy way to fix it is just change your mac.
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Old 12-27-2007, 05:41 AM   #5
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Default Comcast blocking Mac Addresses?

If they block your router, you can always "clone" a mac address from a working NIC onto the router to make it work.
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Old 12-27-2007, 10:46 AM   #6
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Default Comcast blocking Mac Addresses?

Originally posted by: fleabag
If they block your router, you can always "clone" a mac address from a working NIC onto the router to make it work.
Or make one up. But I don't know if that's the legitimate way or not...
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