Fedora and Qwest

Mikkel L. Ellertson mikkel at infinity-ltd.com
Thu May 17 00:02:31 UTC 2007

Tim wrote:
> On Wed, 2007-05-16 at 15:14 -0500, Mikkel L. Ellertson wrote:
>> One thing to be careful about is that you use the same NIC for all
>> the tests. Just about every Cable/DSL modem I have run into will
>> "remember" the first NIC it gave the DHCP lease to, and will not
>> give one to a different NIC unless you power-cycle it. 
> Will probably not give the *same* IP to a different NIC.  Most will give
> a different IP to a different NIC.  That's normal operation.
> Some won't give any IPs to new NICs as a security feature, but that
> tends to be something that you set up.
If you were talking about routers, I would agree with you. But the
DSL/cable modems I have run into have been configured to give out a
DHCP lease to the first MAC address they see after power-up, and
ignore any other MAC address. You have to power-cycle them to get
them to talk to another MAC address. There used to be some that
required the ISP to reset the modem before it would talk to another
MAC address, but those are rare now days.

For that matter, I am using one of the DSL modems like that right
now - if I unplug the router, plug the desktop directly into it, and
boot the desktop, it will ignore the DHCP request from the desktop.
But if I plug in the laptop, it will give it one. (The router clones
the laptop MAC address.) The modem is configured to do PPPoE to the
ISP, so the laptop uses the some configuration when plugged directly
into the modem, or through the router. (I could also configure the
router to do PPPoE instead of the modem.)

I have lost count of the different DSL and cable modems I have run
into that function this way. The only ones that have not are the
ones that combine a modem, firewall, and multi-port router into one


  Do not meddle in the affairs of dragons,
for thou art crunchy and taste good with Ketchup!

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