Spock_rhp
join:2009-07-11
Hollywood, FL
| [Connectivity] Comcast & Home Networks -- setup lessons
Just had lots of "fun" setting up my Comcast supplied DPC2100R2 cable modem and pre-existing router.
Called Comcast tech support three times and got wrong answers three times, so here's what I discovered courtesy of BBR and dslreports.com
Comcast memorizes the MAC address of the computer or other device that is connected to the modem when the modem is initialized. Thereafter, It will NOT allow a cable connection to any device which displays a different MAC address.
Now, since many routers [mine included] prevent accessing the modem page [192.168.100.1 for this modem] through the router, if you ever need to access the modem, you have to bypass your router temporarily and connect the modem directly to the computer.
With Comcast [also Cox cable], this will not allow the Internet to work UNLESS the MAC address it has memorized is the one your computer displays. This means you MUST do the following:
1. when setting up your router, make certain SURE that your main computer's MAC address is 'cloned' into the router. Some routers call this, "use computer's MAC address". This is done from your router's setup or admin screen.
If you ever replace your router, the new one will NOT work until you do this first step. [And, from my experience, the Comcast tech help people won't know why and will try to blame the router.]
2. always have Comcast initialize the modem while it is directly connected to your main computer -- the one the router will report the MAC address of. This way, if your router dies or is suspect, you can disconnect the router and connect your computer directly to the modem to check if the modem is actually working, or to access the modem's signal reports.
3. if you ever get a new computer, you have to FIRST clone the new computer's MAC address into the router and THEN call Comcast and have them reset the cable modem to recognize the new MAC address in the router.
If, for some reason that escapes me, you ever try to directly connect a different device to the cable modem [Xbox 360 anyone?] it will NOT work until after you do step three over again. And if you switch back, you'll have to do it again. [Get a router and save yourself the hassle; they're cheap enough these days.]
GL to all of you who, like me, didn't know these details about Comcast's system and tried to get them to help you over the telephone. |
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nate1234
join:2008-08-21
Moorestown, NJ
 ·Comcast
| I have never had to do any of these things, maybe your modem requires these things? I can change my MAC of my router, and the modem just gets a new IP, and continues to work. What kind of router do you have? I have never heard of anyone else having to do MAC address cloning in order to connect other devices to their modem. |
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EG
The wings of love
Premium
join:2006-11-18
Union, NJ
1 edit | reply to Spock_rhp
said by Spock_rhp  :Comcast memorizes the MAC address of the computer or other device that is connected to the modem when the modem is initialized. Thereafter, It will NOT allow a cable connection to any device which displays a different MAC address. That is true, but a powercycle will erase the MAC addy cache and allow another device to be connected to a modemNow, since many routers [mine included] prevent accessing the modem page [192.168.100.1 for this modem] through the router, if you ever need to access the modem, you have to bypass your router temporarily and connect the modem directly to the computer. Why do you say "many routers" ? That's not true.. I've had 7 different routers and none of them have ever had any problem allowing a connection to a modem's built in web server at that addy...With Comcast [also Cox cable], this will not allow the Internet to work UNLESS the MAC address it has memorized is the one your computer displays. This means you MUST do the following: 1. when setting up your router, make certain SURE that your main computer's MAC address is 'cloned' into the router. Some routers call this, "use computer's MAC address". This is done from your router's setup or admin screen. Not necessary.If you ever replace your router, the new one will NOT work until you do this first step. [And, from my experience, the Comcast tech help people won't know why and will try to blame the router.] A powercycle operation of the modem will take care of this.2. always have Comcast initialize the modem while it is directly connected to your main computer -- the one the router will report the MAC address of. This way, if your router dies or is suspect, you can disconnect the router and connect your computer directly to the modem to check if the modem is actually working, or to access the modem's signal reports. Not necessary3. if you ever get a new computer, you have to FIRST clone the new computer's MAC address into the router and THEN call Comcast and have them reset the cable modem to recognize the new MAC address in the router. Not so, and not necessary. A powercycle operation of the modem is necessary.If, for some reason that escapes me, you ever try to directly connect a different device to the cable modem [Xbox 360 anyone?] it will NOT work until after you do step three over again. And if you switch back, you'll have to do it again. Not necessary. I do agree with using a router for it's other benefits ! GL to all of you who, like me, didn't know these details about Comcast's system and tried to get them to help you over the telephone. This is NOT the way "CC's system" functions.. |
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koshoka
join:2006-12-01
Pottsville, PA | Yeah, what EG said.
In short...
Unplug modem->hook up router->plug in modem->allow modem to connect->turn on router. |
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dearlord
@comcast.net | reply to Spock_rhp
I don't mean any disrespect or insult to this but honestly you do not know what you are talking about and have mentioned quite a few steps that are not required and can be so easily fixed by a simple modem reset. |
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Spock_rhp
join:2009-07-11
Hollywood, FL | reply to Spock_rhp
power cycled the modem three times; including for over 10 minutes, and it still did not clear the MAC address cache you are referring to.
defective modem? |
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EG
The wings of love
Premium
join:2006-11-18
Union, NJ
2 edits | said by Spock_rhp :power cycled the modem three times; including for over 10 minutes, and it still did not clear the MAC address cache you are referring to. defective modem? Possibly. Have you tried removing the coax cable, and the ethernet cable, and leaving the modem unplugged for 10 minutes or so ?
You have already made a general/sweeping statement that this is the way it is on their entire system and/or in your area in another thread.. |
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Spock_rhp
join:2009-07-11
Hollywood, FL
| reply to Spock_rhp
disconnected all cables for the 10 minutes ... Comcast called me back when was time to reconnect ... would not function and they concluded that my router was defective ["problem belongs to customer -- get out of here"].
{Router is an SMC and is over 5 years old now. Had several before this one of other brands and all would not permit accessing the modem via the router. if this is a firewall feature, I do not know how to disable it and it isn't in the manual.} |
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nate1234
join:2008-08-21
Moorestown, NJ | Maybe get a new router? Maybe newer routers allow this. Try a Linksys WRT54GL, they are like $50 |
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EG
The wings of love
Premium
join:2006-11-18
Union, NJ
1 edit | reply to Spock_rhp
said by Spock_rhp :disconnected all cables for the 10 minutes ... Comcast called me back when was time to reconnect ... would not function and they concluded that my router was defective ["problem belongs to customer -- get out of here"]. What model # is the SMC ?
Can you post the output of an ipconfig /all with it in the path ? |
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GoAheadPushIt
@comcast.net | reply to Spock_rhp
Maybe pressing the modem's reset button would clear the previous MAC address?
»www.cisco.com/web/consumer/suppo···5527.pdf |
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