Comcast blocking Mac Addresses?

unpossible

Member
Jan 18, 2005
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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?
 

Fardringle

Diamond Member
Oct 23, 2000
9,184
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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? ;)
 

w0ss

Senior member
Sep 4, 2003
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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.
 

fleabag

Banned
Oct 1, 2007
2,450
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If they block your router, you can always "clone" a mac address from a working NIC onto the router to make it work.
 

TC10284

Senior member
Nov 1, 2005
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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...