Re[2]: [Xitami] IP numbers,etc.

[Paul Reid]

> each NIC has a specific identifier code, somehow (and I have no
> clue how)

Every ethernet NIC has a unique serial number (MAC number) burned
into ROM. I have not disassmebled any cable-modem boxes but they
must have the same or similar functionality (possibly in the cable
head-end rather than the modem, considering the origins of 2-way
cable TV).

> DHCP is designed to assign the same IP to the same adapter if the
> network permits it.

DCHP uses whatever rules the admin sets.

Traditionally, you get ("lease") an IP for a period of time, an hour
or a week or "indefinite", and can renew the lease when it expires.
And traditionally it provisionally reserves the MAC=IP association
for hours or weeks after the DCHP lease expires unrenewed. If you
come back on-line within that time, and the DCHP server has not been
forced to give "your" IP to another NIC, then you get the same one
again.

However, give some people a tool and they abuse it. Some home ISP
services aggressively thrash DCHP so you won't keep the same IP
number for very long. After all, they sell fixed IP service at a
higher price, so why let you have the same thing for cheap?

 -PRR