[nSLUG] Eastlink cable modem access

Jon me at jonwatson.ca
Thu Jan 31 14:08:36 AST 2008


On Jan 31, 2008 2:20 PM, Jeff Warnica <jeff at coherentnetworksolutions.com>
wrote:

>
>
> Quoting Jon <me at jonwatson.ca>:
>
> > Interesting. Granted, I don't spend a lot of time watching DHCP logs,
> but I
> > would think that the second example is more indicative of a 'normal'
> DHCP
> > request as it is a broadcast request on port 67. This is designed to hit
> any
> > DHCP server on the network in the hopes that it will give out an
> address.
> >
> > Given that a computer without an IP address cannot communication on a
> TCP/IP
> > network. I can't see how a DHCP request to a specific address (like  in
> your
> > first snippet) would succeed. Perhaps it's a refresh request in that the
> > interface already has an IP assigned to it and can therefore query a
> > specific DHCP server.
>
>
> True when you the client is starting out, and is totally ignorant of
> itself and the world.. However, when refreshing a lease you first ask
> who told you last time.
>

I searched the RFC for this and was failing, but finally found it. You are
correct, but I'm sure you knew that.

Now I go back to work.

>From http://www.faqs.org/rfcs/rfc2131.html

4.4.5 Reacquisition and expiration

   The client maintains two times, T1 and T2, that specify the times at
   which the client tries to extend its lease on its network address.
   T1 is the time at which the client enters the RENEWING state and

   attempts to contact the server that originally issued the client's
   network address.  T2 is the time at which the client enters the
   REBINDING state and attempts to contact any server. T1 MUST be
   earlier than T2, which, in turn, MUST be earlier than the time at

   which the client's lease will expire.
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