Subject: newbie question, querying dhcp servers (DHCPINFORM?)

From: Andrew Wallace <[email-masked]>
Date: Fri, 7 Apr 2000 14:21:50 +1000

I want to find out the host names associated with an IP address on our
network which uses a DHCP server.

Can I send a query to a DHCP server that will return a host name from the IP
address?  

If not, is there anyway I can find the host name from the IP in a DHCP
environment?

Looking at RFC2131 I was wondering what would happen if I send a DCHPINFORM
message to the server requesting the hostname details (with the giaddr field
to the address that I would like the response sent to).  
How does this sound?

Do any DHCP servers support any sort of IP-to-name resolution?  (by the way
we're using a Windows NT DHCP server v4.1)

I would appreciate any help/thoughts,

Thnaks,
Andrew Wallace

Phoneware Communication Systems Pty Ltd
Telephone:	(03) 9210 4263
Fax:        (03) 9887 6199
Email:		[email-masked]
www:        http://www.phoneware.com.au

---

From: Ted Lemon <[email-masked]>
Date: Thu, 06 Apr 2000 22:05:11 -0700

DHCP doesn't do that - you need DNS.  Do a DNS query taking the IP
address, reversed, plus .in-addr.arpa.  So if your IP address is
1.2.3.4, look up a PTR record for 4.3.2.1.in-addr.arpa.  There's no
requirement that this be associated with a name, but most network
administrators do set up PTR records like this.

The nslookup command to do this, BTW, would be:

nslookup
...
> set type=PTR
> 4.3.2.1.in-addr.arpa.
...

			       _MelloN_