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List:       dhcp-client
Subject:    Re: DHCPINFORM in client?
From:       Jan Vilhuber <vilhuber () cisco ! com>
Date:       2000-08-30 21:39:24
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On Wed, 30 Aug 2000, Ted Lemon wrote:

> 
> > I noticed that in version 3 (pulled from anon cvs), there's support for
> > DHCPINFORM in the server, but not the client. Any idea why not? Are there
> > pitfalls that prevent an easy implementation of DHCPINFORM?
> 
> What do you want to do with it?

I have a linksys firewall between me and the cable modem. It does dhcp.
Today, apparently the cable provider changed addresses whlesale (from a 206
subnet to a 63 subnet!!), and all my hardcoded dns address stopped working.
That cost me almost half an hour to figure out (due to other problems as
well), and I got to thinking, it would be REALLY nice if I could simply pull
the DNS address from the linksys box (I doubt it supports DHCPINFORM, but
that's another problem). That way, the boxes that I have statically
configured with an ip-address can pull the dns information without actually
being dhcp clients (I want them static, and the linksys doesn't support MAC
address to ip-address mapping).

That's apparently what DHCPINFORM is for afterall ;)

Yes, there's other ways I could accomplish this same thing, but either I'll
have to run dns servers on all my linux boxes (the dhcp windows machines
don't matter, in more ways than one ;), or keep ONE machine up all the time
as a dns cache (costs electricity and fan-noise), etc. None of them are
particularly appealing. Running a dns server on all linux boxes seems like an
idea, but really: DHCPINFORM was apparently invented to do exactly what I
want to do with it :)

> The client is really written with
> the idea of configuring interfaces, so using it to do DHCPINFORM would
> require some serious thinking.
> 
Or maybe a new command altogether, that does the DHCPINFORM, twiddles the
right files (/etc/resolv.conf in this case) with the information retrieved,
and exits. I don't know enough about the DHCPINFORM to know if there's a
lifetime associated with that information (you mean I'll have to read the
rfc.. awwww). One could then run this mythical 'dhinform' command at boot-up,
or via cron periodically or something.

> > Are there plan to put the capability to do a DHCPINFORM query into the
> > client? If not, I guess I better start writing the code ;)
> 
> By all means!   :')
> 
I'll take a look.

jan
 --
Jan Vilhuber                                            vilhuber@cisco.com
Cisco Systems, San Jose                                     (408) 527-0847


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