[ale] Re-send: Opinions on Cable versus DSL

Dan Newcombe Newcombe at mordor.clayton.edu
Wed Jul 25 22:53:48 EDT 2001


On Tue, 24 Jul 2001, Wandered Inn wrote:
> Dan Newcombe wrote:
> >  a) when you get an ip address, the server stores your MAC.  Next time
> > you request an address, it looks to see if it has serviced you before.  If
> > it finds your MAC in it's tables, and that IP is still open, it gives it
> > back to you.
> If, it's still available.  I personally do not know how it works, just
> what I've read from the HOWTO.  If this is accurate, I would say the
> HOWTO is a bit misleading, as I would not call the process you've
> indicated above as 'random.'

I guess it would depend on the DHCP server implementation.  According to
RFC2131, when the client requests an IP, it'll usually request for the
address it had the last time it had a DHCP address.  The RFC says that IF
that address is avail (can't be pinged) and is within it's range of
addresses, it should accomodate the request, otherwise, give out another
"random" ip.  I guess I was wrong stating it as the server remembers you
(which while the RFC doesn't say anything about it, a server could
probably implement it that way), but if the IP address you had last time
is free, then 99% of the time you should get it again.

> Understood, but I would be surprised if the isps are providing fixed
> ips, as (at least BellSouth) claims that this is part of a security
> issue.  If your ip is not static, then it's harder for a hacker to find
> you multiple times.

Yeah...that makes it real secure :)  Chances are they found you by
portscans anyway :)

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