DHCP client questions

[David Horn]

On Sun, Sep 20, 2009 at 3:19 PM, stan <stanb at panix.com> wrote:
> We have been bought out, and the new powers that be, are changing things.
> They have decreed that there shall be no static entries in their DNS
> servers. They are using $MS DHCP/DNS servers. I have a corporate supported
> Win XP laptop, which I can plug in at various places in the network. It
> gets different IP addresses, based upon where it physically is, but always
> comes up with the same name.

The question is whether by the "same name" you are referring to a dns
lookup, a wins lookup, or a nbns broadcast query, or all of the above
;)

>
> I have several machines (such as a mailserver) which _MUST_ have fixed
> names. I have played around with /etc/dhcllient.conf, but not managed to
> get this working. I can get IP addresses, and various things such as
> default routers, and DNS servers, but I have not managed to get the
> suggested name put in their DNS.

try running:

 tcpdump -r filename.pcap -vvv port bootpc

in order to get a nice decode of your dhcp session.  This will contain
by the client discover/request/ack, and the server offer packets.

>
> I have captured packet traces with wireshark from the laptop, and from the
> FreebSD client, and I am putting these up at http://beachcave.net/pdumps.
>
> I would really appreciate it if someone more familiar with DHCP that I
> could take a look at theses.

Your windows capture clearly shows a dhcp option 12 with the short
name, and dhcp option 81 with FQDN

           Hostname Option 12, length 10: "CHSLSBROWN"
            FQDN Option 81, length 31: "CHSLSBROWN.kapstonepaper.com"
            Vendor-Class Option 60, length 8: "MSFT 5.0"
            Parameter-Request Option 55, length 11:
              Subnet-Mask, Domain-Name, Default-Gateway, Domain-Name-Server
              Netbios-Name-Server, Netbios-Node, Netbios-Scope, Router-Discovery
              Static-Route, Classless-Static-Route-Microsoft, Vendor-Option
            END Option 255, length 0

Your freebsd captures show dhcp option 12 with the FQDN.  You need to
try using option 12 and option 81 just like in windows land.  You may
even need to put in the Vendor-Class and/or others to duplicate the
windows request, but try one item at a time.

Try adding these to your dhclient.conf as needed.  Take the time to
look at the man page for dhclient.conf, and dhcp-options, and also
take a look at the full defined option numbers here:
http://www.iana.org/assignments/bootp-dhcp-parameters/

Good Luck.

--Dave H