Different NIC Cards

Different NIC Cards
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Subject Author Date
Different NIC Cards Charles Newman 09-04-2007
---> Re: Different NIC Cards Gene S. Berkowi ..09-04-2007
Posted by Jbob on September 4, 2007, 9:53 pm
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>
>
>
> I notice that Comcast assigns IPs based on the NIC card. As I
> was preparing to switch to DSL, I hooked one computer to the
> cable modem and the other to the DSL, to make sure I have
> everything connected right, by accessing the DSL from my
> cable modem, and I see that Comcast gave me a different
> IP number on a different computer with a different NIC
> card. How does Comcast know that I am logging on with a
> different NIC card and a different computer?
>
> ]


The WAN IP is issued not really to the NIC card but to the first network
device it sees. It is based on the MAC address of the device. Every(or
most anyway) network accessing device used a MAC address for identification.
If you hook up a SOHO router it will issue the WAN IP to that device. If
you hooked up a console game it would get a different IP.



NMFall 20%
Posted by Gene S. Berkowitz on September 4, 2007, 11:38 pm
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says...
> I notice that Comcast assigns IPs based on the NIC card.

No, you're mistaken. Comcast generally hands out dynamic IP addresses,
which are "leased" for a period of time. The particular addresses are
handed out randomly from a pool. When the lease expires, or you shut
off your cable modem, the address is returned to the pool and issued to
someone else. If you never turn off the cable modem, the lease can be
"renewed" when it expires, so it is possible to maintain the same
address for weeks or months.

--Gene

Posted by Tom Stiller on September 5, 2007, 7:30 am
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> says...
> > I notice that Comcast assigns IPs based on the NIC card.
>
> No, you're mistaken. Comcast generally hands out dynamic IP addresses,
> which are "leased" for a period of time. The particular addresses are
> handed out randomly from a pool. When the lease expires, or you shut
> off your cable modem, the address is returned to the pool and issued to
> someone else. If you never turn off the cable modem, the lease can be
> "renewed" when it expires, so it is possible to maintain the same
> address for weeks or months.
>

Comcast procedures are not uniform across the country. In my area, if I
attach a device with a different MAC address to the cable modem, I will
be assigned a different IP address. If I reattach the original device I
will be assigned the IP address that was last assigned to that device.

--
Tom Stiller

PGP fingerprint = 5108 DDB2 9761 EDE5 E7E3 7BDA 71ED 6496 99C0 C7CF

Posted by Dana on September 5, 2007, 3:03 pm
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>
>> says...
>> > I notice that Comcast assigns IPs based on the NIC card.
>>
>> No, you're mistaken. Comcast generally hands out dynamic IP addresses,
>> which are "leased" for a period of time. The particular addresses are
>> handed out randomly from a pool. When the lease expires, or you shut
>> off your cable modem, the address is returned to the pool and issued to
>> someone else. If you never turn off the cable modem, the lease can be
>> "renewed" when it expires, so it is possible to maintain the same
>> address for weeks or months.
>>
>
> Comcast procedures are not uniform across the country. In my area, if I
> attach a device with a different MAC address to the cable modem, I will
> be assigned a different IP address. If I reattach the original device I
> will be assigned the IP address that was last assigned to that device.

Seems there is some confusion here anout how DHCP works.
The NIC MAC address is assigned an ip address from a pool. Depending on how
the ISP is set up for their lease time on the address, it is possible to get
the same address after a shutdown. Again this is dependent on the
configuration of the ISP and how many users are contending for the IP
addresses.
So above where you say you received the same address that was assigned to
that device, is very possible with dhcp. The above is not saying you are
being assigned a static IP from your ISP.
>
> --
> Tom Stiller
>
> PGP fingerprint = 5108 DDB2 9761 EDE5 E7E3 7BDA 71ED 6496 99C0 C7CF



Posted by Tom Stiller on September 5, 2007, 4:09 pm
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> >
> >> says...
> >> > I notice that Comcast assigns IPs based on the NIC card.
> >>
> >> No, you're mistaken. Comcast generally hands out dynamic IP addresses,
> >> which are "leased" for a period of time. The particular addresses are
> >> handed out randomly from a pool. When the lease expires, or you shut
> >> off your cable modem, the address is returned to the pool and issued to
> >> someone else. If you never turn off the cable modem, the lease can be
> >> "renewed" when it expires, so it is possible to maintain the same
> >> address for weeks or months.
> >>
> >
> > Comcast procedures are not uniform across the country. In my area, if I
> > attach a device with a different MAC address to the cable modem, I will
> > be assigned a different IP address. If I reattach the original device I
> > will be assigned the IP address that was last assigned to that device.
>
> Seems there is some confusion here anout how DHCP works.
> The NIC MAC address is assigned an ip address from a pool. Depending on how
> the ISP is set up for their lease time on the address, it is possible to get
> the same address after a shutdown. Again this is dependent on the
> configuration of the ISP and how many users are contending for the IP
> addresses.
> So above where you say you received the same address that was assigned to
> that device, is very possible with dhcp. The above is not saying you are
> being assigned a static IP from your ISP.
> >

I never said that I was assigned a static IP address. What I said was
that I got a different IP address for each different MAC address I
connected to the cable modem, but that the IP/MAC address pairings were
retained no matter how many times I switched devices or re-synched the
modem.

--
Tom Stiller

PGP fingerprint = 5108 DDB2 9761 EDE5 E7E3 7BDA 71ED 6496 99C0 C7CF

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