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nivar

join:2006-01-06
Bremerton, WA

Comcast filtering MAC addresses

Greetings all,

History:
Last Friday my home network went off-line for the first time in 9 months for no apparent reason. After a hour or so of diagnostics, reboots, restarts, etc... I connected my laptop directly to the Comcast modem and found out that my IP Address changed for the first time in over a year. Not a big deal, after all that is what DHCP is suppose to do.

However, I was unable to get a IP address into my router, but my laptop can get and IP just fine. I cloned my MAC address from my laptop to the router and I got a IP instantly, but if I turn off cloning I loose the IP address. I swapped from my Cisco router to a Linksys, same thing occurred. I swapped from my Linksys to and old D-link same thing occurred. I tried cloning my Desktop computer's MAC and I was unable to get a IP from Comcast. We tried both of my room-mates computers MAC's and those too failed.

I contacted Comcast and explained the problem that the router was not being issued an IP address and that I couldn't get online. They started in with the whole "did you restart your router? Have you changed your configurations?" blah blah blah. I told them it worked just fine before last Friday when I was issued a new IP address via DHCP. And I explained that I could get online if I cloned my Laptops MAC into the router. They told me that was what I was suppose to do. I told them that I didn't want to do that because I didn't want to have THAT MAC address blocked too because it was the only one working. They just told me that I would have to contact their home networking division. Who appearently is not available for comment (well at least they dont answer their phone.)

Problem: Currently I am connected to the internet using my Laptop's MAC... but now, I cannot connect my Laptop via wired connection because of conflicts between my laptops burned in MAC and my routers cloned MAC.

Question: Clearly Comcast is doing some serious MAC address filtering. So how the hell do I get a MAC address that will allow me an IP address from Comcast, and allow my Laptop to connect to the network wired so I can transfer files to and from my desktop?


gdio53

join:2000-07-30
Feeding Hills, MA
The modem will remember the last device plugged in, and you're only allowed 1 MAC, so you'll need to clear the modem of the laptop MAC
Power off the modem and disconnect any devices plugged into it.
Wait 1 minute before restoring power to the modem.
Plug in your router.
Reconnect your other devices to the router. You should have an IP now.
If you don't, it could be that the router is bad, repeat the power off procedure trying another router.


beerbum
Premium
join:2000-05-06
Reading, PA
kudos:1
Reviews:
·Comcast
reply to nivar
1) shut down all PC's, shut off router, shut off modem (if emta remove battery also)

2) plug router's ethernet into modem
3) connect PC(s) to router
4) turn on modem, wait for sync
5) turn on router
6) turn on PC(s)

No cloning needed, whenever you switch devices connected to router you need to turn off and restart modem, otherwise it will not recognize the "new" device.

optional: instead of using dhcp, set your pc's to use a static address, usually 192.168.1.x with the gateway 192.168.1.1 (check router documentation since some use 192.169.0.x instead of 1.x).
--


a mind is a terrible thing...


JahsDisciple
Living my life like it's golden
Premium
join:2007-07-07
Baltimore, MD
kudos:1
said by beerbum:

1) shut down all PC's, shut off router, shut off modem (if emta remove battery also)

2) plug router's ethernet into modem
3) connect PC(s) to router
4) turn on modem, wait for sync
5) turn on router
6) turn on PC(s)

No cloning needed, whenever you switch devices connected to router you need to turn off and restart modem, otherwise it will not recognize the "new" device.

optional: instead of using dhcp, set your pc's to use a static address, usually 192.168.1.x with the gateway 192.168.1.1 (check router documentation since some use 192.169.0.x instead of 1.x).
agreed. but if an emta, you shouldnt have to take out the battery. there's a reset button you can hold in for a few seconds and then wait for it to boot back up before booting up the router.
--
"Nothing in all the world is more dangerous than sincere ignorance and conscientious stupidity." Rev. Dr. Martin Luther King, Jr.

Kearnstd
Space Elf
Premium
join:2002-01-22
Mullica Hill, NJ
kudos:1
infact it is suggestted that the customer never remove the battery. that reset button on an EMTA is ment for the causal resets.
--
[65 Arcanist]Filan(High Elf) Zone: Broadband Reports

ats

join:2008-11-14
Vallejo, CA
kudos:1
reply to JahsDisciple
resetting the emta with the reset button should be the last resort cause by doing that,the emta resets to the original factory config and whatever updates on the firmware that were downloaded will be erased.

yurkinator

join:2007-07-30
Newark, DE
I have never seen an MTA lose firmware updates when reseting it.

nivar

join:2006-01-06
Bremerton, WA
reply to nivar
That did the trick. It was the battery. I didn't even know that modem had one. Once I pulled the battery, unplugged the thing and reset everything, my router was able to get back online all on its own.

Because Comcast installed the modem, I didn't get any instruction manual, so I had nothing to refer to, but appearantly the thing has a battery that will last for 8 hours or so, so that my phones will work for a while in the event of power outage.

I find it disturbing and slightly alarming that the Comcast tech I talked to, didn't know to pull the battery, or that pulling the battery was the solution.


dadkins
Can you do Blu?
Premium,MVM
join:2003-09-26
Hercules, CA
kudos:18

2 edits
reply to ats
said by ats:

resetting the emta with the reset button should be the last resort cause by doing that,the emta resets to the original factory config and whatever updates on the firmware that were downloaded will be erased.
Current Firmware:

Firmware Build and Revisions
Firmware Name: TS050237C_112907_MODEL_4_5_6
Firmware Build Time: Thu Nov 29 17:03:00 EST 2007

Reset, BRB

EDIT: Held Reset button for 20 seconds - for kicks!

Now current firmware:

Firmware Build and Revisions
Firmware Name: TS050237C_112907_MODEL_4_5_6
Firmware Build Time: Thu Nov 29 17:03:00 EST 2007

No change.

Worst case I have seen, personally, when battery is removed - you may have to reset anyways to get telemetry back on the battery.

--
Think outside the Fox... Opera

nivar

join:2006-01-06
Bremerton, WA
reply to nivar
On a different, but related note: Anyone have any idea why the modem decided to dump or block the MAC address originally?

I wouldn't think that an IP change via DHCP would have anything to do with that.


dadkins
Can you do Blu?
Premium,MVM
join:2003-09-26
Hercules, CA
kudos:18
Modems will usually remember the last item's MAC address that was connected.
If you change items without resetting/powercycling, the MAC will be different than what is in memory and connectivity will be denied.

Resetting or powercycling will erase the memory and it will have to remember the new item.

Should work fine then.
--
Think outside the Fox... Opera

nivar

join:2006-01-06
Bremerton, WA
reply to nivar
I was in class at the college when my IP address changed here at the house. There was nobody home to cycle the power on either the router or the modem. Yet it blocked the MAC address and wouldn't give a new IP address. It picked up my laptops MAC address hours after the system was effected, and then locked that MAC in and wouldn't accept any other.

So why did it drop and block my router MAC in the first place?

I am just trying to understand everything that happened so that I can be prepared for the next time things go to hell.

jabuqua

join:2004-10-10
Beverly Hills, CA

1 recommendation

reply to ats
said by ats:

resetting the emta with the reset button should be the last resort cause by doing that,the emta resets to the original factory config and whatever updates on the firmware that were downloaded will be erased.
You got that reversed. As was already stated, the reset button must be used for resetting when switching devices. The last resort is to remove the battery & powercycling. You're only advised to do that once everything else fails due to the chance of loosing the dial tone since the modem does a more extensive check during the boot up sequence when the battery has been removed.

Nivar: WA has been undergoing the whole 3.0 upgrade so this might have been related... ?

nivar

join:2006-01-06
Bremerton, WA
reply to nivar
Ah... upgrade.

Upgrade = instability and wackyness ensues

Got it.

Thanks alot everyone for your help.


EG
The wings of love
Premium
join:2006-11-18
Union, NJ
kudos:10
reply to beerbum
said by beerbum:

whenever you switch devices connected to *router* you need to turn off and restart modem, otherwise it will not recognize the "new" device.
Do you mean the *modem* here ?


dadkins
Can you do Blu?
Premium,MVM
join:2003-09-26
Hercules, CA
kudos:18
reply to nivar
Comcast can reset modems from their side - usually.
A power "hiccup" could have occurred.
Unknown.

Either way, a reset or powercycle would have fixed it(still will if it ever happens again).

YOU HAVE TO ERASE THE MEMORY or no other machine's MAC will be accepted.
Resetting or powercycling is the only way to erase the memory.
--
Think outside the Fox... Opera

Kearnstd
Space Elf
Premium
join:2002-01-22
Mullica Hill, NJ
kudos:1
reply to Kearnstd
said by Kearnstd:

infact it is suggestted that the customer never remove the battery. that reset button on an EMTA is ment for the causal resets.
it would just redownload the correct firmware if that happened.
--
[65 Arcanist]Filan(High Elf) Zone: Broadband Reports

calathea

join:2001-12-29
Scio, OR
Reviews:
·CenturyLink
reply to nivar
Hi Nivar, I posted this as a new post before I saw yours -- it sounds like the same thing and we are both in the Pacific Northwest. --

We have the Comcast Triple Play. It has been reliable since we got it several months ago. Today the internet connection suddenly disappeared. I will not bore you with the blow-by-blow detail of the two calls to Comcast and the 27 shutdown/startups of the PC, nor the myriad router power cycles and resets. Of the two Comcast excuses, one was old "your router messed up" and one was new "your PC booted up too fast."

I had to call Comcast back on a cell phone because we have phone service from them. In order to get the PC to connect, they had to reset their modem box from their side, which would have ended the phone call. After they did that, the direct connection to the PC started working. But the router still couldn't get an IP address from Comcast.

What I ended doing was to upgrade the router firmware, reset it back to factory defaults, and clone the MAC address. Then it finally started working. It took half a day. The exercise also included my husband going out and buying a new router because I had despaired of ever getting it working again, then taking the new router back because I had fixed it by the time he got home.

We speculate that Comcast reconfigured something, then somehow wouldn't reprovision the router. It had to reprovision the PC directly. Will never know for sure.


asdMD29455

@comcast.net

1 recommendation

reply to nivar
well this is interesting indeed. Yesterday my comcast connection exhibited the same symptoms. I called comcast, no help. When plugging the cable modem directly into the computer worked, comcast declared their duty fulfilled. However, our router couldnt get a connection. so thinking we had a bad router, we bought a new WRT54G... same thing. so we replaced the motorola surfboard modem that comcast gave us with an RCA one from comcast... same thing. But cloning the mac address of a computer on the network solved the problem. our 3 macs, 2 windows machines, and 2 linux machines all got their internet back at once.

Weird... same place, same time, same problem. I agree... comcast changed something somewhere and things went haywire...