Re: DHCP in a Windows 2000 domain - udhcpc

[Ajit Warrier <unixajit yahoo com>]

Rick,

Thanks a lot for that email. It must have taken up a
lot of your time! What you say makes a lot of sense
and I think I need to read up on DHCP. In the mean
time I will try what you have said.

Thanks for your time.

Ajit

--- Rick Stevens <rstevens vitalstream com> wrote:
> Ajit Warrier wrote:
> > --- Rick Stevens <rstevens vitalstream com> wrote:
> > 
> >>Ajit Warrier wrote:
> >>
> >>>I am the administrator of the Windows DHCP server
> >>
> >>and
> >>
> >>>it was already set as you have described. It
> still
> >>>doesn't work. As in, I get an IP all right but my
> >>>hostname does not get registered. Thanks for the
> >>>interest anyway.
> >>>
> >>>A friend has suggested that something called
> >>
> >>udhcpc
> >>
> >>>could do this. I am searching for it. If it is of
> >>
> >>any
> >>
> >>>use, I will post to the list. Of course, if some
> >>
> >>one
> >>
> >>>knows about this, please let me know.
> >>
> >>Never heard of that one.  Are you sure the DHCP
> >>server is sending you a
> >>hostname?  It will only be able to update DNS with
> a
> > 
> > 
> > ********************
> > I think the way it works in W2K is that the W2k
> client
> > asks for an IP and once it has received it, the
> DHCP
> > server registers the client hostname and IP with
> the
> > DNS server, I dont know if the DHCP server sends
> the
> > hostname to the client but it sure sends it to the
> DNS
> > server. Is there a way I can find out?
> 
> That's the way it works in _any_ DHCP environment
> (well, it's supposed
> to work that way).  The DHCP server gives an
> address, gateway, hostname,
> and DNS server info to the client, it then does a
> DDNS update to the
> DNS server inserting the appropriate A and PTR
> records into DNS.  The
> client should NEVER have to do that.  If it does,
> then there's a severe
> screwup in the design of the network servers.
> 
> The client _can_ ask for a specific hostname to be
> given, but there's
> no rule that says the DHCP server has to abide by
> that request. On the
> other hand, the client is required to live by what
> the DHCP server says.
> It can alias the hostname in its /etc/hosts file,
> but basically what
> the DHCP server says, goes.
> 
> > But doesn't the hostname of the client go from the
> > client to the DHCP server rather than from the
> DHCP
> > server to the client?
> 
> No.  As I said above, the client can _ask_ for a
> specific host name, but
> the DHCP server does NOT have to honor that request.
>  The hostname that
> the server _does_ give is what will be inserted into
> DNS (if DDNS is
> enabled).
> 
> If the server honors the client request, the name
> returned in the DHCP
> lease will be what the client asked for.  If the
> server does NOT honor
> the request, the name will be whatever the server
> deems appropriate and
> the client will have to deal with that fact.
> 
> If the hostname is important (e.g. print queues, X),
> one can create a
> post-lease script that picks up the IP address and
> adds a record to the
> /etc/hosts file to "alias" the hostname they want to
> the IP address they
> got.  As far as DNS is concerned, the alias doesn't
> exist (there's no
> CNAME record), so the outside world will only know
> the client by the
> name the DHCP server gave it, but your print queues
> and X-windows stuff
> will work properly since the hostname will resolve
> to the current IP
> address via the hosts file.
> 
> You can alternately insert a /etc/hosts line that
> equates 127.0.0.1 to
> your desired host name and things will always work
> locally regardless of
> what DHCP does to you.  In that case, make sure you
> set up your DHCP
> client to NOT set the hostname to that given by the
> DHCP server (dhcpcd
> does NOT set the hostname by default, the "-H"
> option turns that on).
> 
> As a side note, the client should NEVER be able to
> insert its hostname
> into DDNS--that is reserved for the DHCP server.  If
> a client can do an
> insertion, then the security of the DDNS system is
> SEVERELY compromised.
>
----------------------------------------------------------------------
> - Rick Stevens, Senior Systems Engineer    
> rstevens vitalstream com -
> - VitalStream, Inc.                      
> http://www.vitalstream.com -
> -                                                   
>                 -
> -      "Doctor!  My brain hurts!"  "It will have to
> come out!"       -
>
----------------------------------------------------------------------
> 
> 
> 
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