Re: DHCP in a Windows 2000 domain - udhcpc

[Rick Stevens <rstevens vitalstream com>]

Ajit Warrier wrote:
> Hi Rick,
>
> As far as I can make out from what you say, the DHCP
> server will issue the hostname to the DHCP client and
> if the DNS is Dynamic and properly configured, this
> hostname should get registered with it. I know that
> when a Windows client gets its information from the
> DHCP server, it is properly entered into the DNS
> server as well, so we can assume that the DHCP and the
> DDNS are properly set up.

Probably.  As I said before, I'm not a Windows guy.  They may have
hostnames preloaded into the DNS, too.  I'd be curious to see if
a dig against the DNS works for the hostname BEFORE the client
actually gets its lease.

> This means that the hostname that the DHCP server
> issues to the DHCP client should get registered in the
> DNS server as well whether that is the name the client
> requested for or not. Ok, so far?

Yup, if DDNS is set up properly.

> Well, I am getting an IP from the DHCP server but the
> hostname entry on the DHCP server is blank and there
> is no entry for this IP in the DNS server. When I do
> "hostname" on the DHCP client, it returns the hostname
> that I have set, of course and it does _not_ resolve
> it to the IP (which is expected since this name has
> not registered with the DNS).

You don't have the "-H" option set on the dhcpcd client.  By default,
dhcpcd will _not_ set the hostname to the one sent by the DHCP server.

> I guess what I asking for boils down to this -
> 1. How can I find out what name is being issued to the
> DHCP client?

You can do a tcpdump off the ethernet port to see the dialog between
the DHCP server and client.  Something like:

	tcpdump -a -s 1024

should show it.

> 2. Can I change the hostname to the one that has been
> issued to the DHCP client, automatically, as soon as
> the client finds out what its hostname is?

Yes, add this to your /etc/sysconfig/network-scripts/ifcfg-eth0 file:

	DHCPCDARGS="-H"

That forces dhcpcd to accept the hostname from the server, assuming
you're using dhcpcd.  If you use dhclient (RH8.0/9), then you need to
make sure the "require=host-name" is in the /etc/dhclient.conf file.
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- Rick Stevens, Senior Systems Engineer     rstevens vitalstream com -
- VitalStream, Inc.                       http://www.vitalstream.com -
-                                                                    -
-                       When in doubt, mumble.                       -
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