Fedora and Qwest

Tim ignored_mailbox at yahoo.com.au
Thu May 17 07:15:52 UTC 2007


Tim:
>> 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.

Mikkel L. Ellertson:
> 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.

I haven't come across that (yet).  I'm familiar with the issue of some
ISPs remembering the MAC of the device that connects to their network
(the DSL modem), but not come across that issue on the client side.

ISP ---- modem/router ---- client PC
         (gets IP from     (gets IP from
         ISP using DHCP)   (modem using DHCP)

All the modem routers I've played with act as an internal DHCP server
that give an IP out to every device connected to it, by default,
automatically.  It'd be a really dumb thing to have to power cycle them
for everything that gets connected to your LAN.

Modems in bridge mode are another matter.  The ISP sees the PC's NIC,
uses its MAC, expects the same one all the time. 

ADSL Modems without a router (i.e. just one LAN port on them) are
something I've not played with.

-- 
(This box runs FC6, my others run FC4 & FC5, in case that's
 important to the thread.)

Don't send private replies to my address, the mailbox is ignored.
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