DHCP question

[David A. Bandel]

On Tue, 9 Jul 2002 04:27:54 -0400
begin  Joel Hammer <Joel at hammershome.com> spewed forth:

> All the verbiage which follows simply leads up to this question: How,
> in the routine course of events, can a dhcp server force a renewal, or
> terminate, an ip number given to a client and reassign it to another
> client before the end of the lease time?  This is what comcast did to
> me, and I am still puzzled by it. 
> 
> Read on for some ramblings.
> 
> Just trying to figure out how my computer interacts with the comcast
> dhcp server. dhcpcd runs all the time on my machine once you start it
> up.
> 
> I am reading RFC2131. It describes in detail how the server and client
> interact.
> 
> No where can I find where the server can force the client to renew or
> rebind prior to the times given in the original lease. That is to say,
> as I understand it, (BIG assumption: understand) the client is the one
> who sends the request for the lease renewal; and, the server cannot
> initiate a lease change prior to the end of the lease. The dhcpcd daemon
> is not listening for the server for messages. In fact, the dhcp server
> cannot initiate a message to the client.  To support this conclusion,
> there is no process listening to port 67 or 68 on my client machine.
> 
[snip]

No, but please reread the part about where a client shuts down and returns
the lease. Windoze users typically restart their computer twice a day, and
normally shut down at least daily.  It's a Windoze habit.  

> 
> As described in another thread, comcast terminated this lease and
> reassigned my ip number without my knowledge. How can comcast tell I am
> running with a static ip, unless they looked at their own database to
> see the lease they assigned me originally?  Assuming they did that, how
> could they reassign my ip number when it was still leased to my
> computer, thereby just cutting me off from the internet, and threatening
> to terminate my account "if this happens again"?
> 

If you have a dhcp server you can force termination of a lease.  If they
forced termination of all leases, then 2 days later checked to see which
IPs were in use, but not in their leases file (because the server checks
to see if an IP is in use before assigning it), then they know who has a
static IP (logically, if Windoze lusers do daily shutdowns).  OK, you're
not a Windoze luser, you're an exception.

Ciao,

David A. Bandel
-- 
Focus on the dream, not the competition.
		-- Nemesis Racing Team motto