INFORM not working properly?

[Glenn Satchell]

>Date: Mon, 26 Mar 2007 19:21:44 -0700
>From: Craig <craig5 at pobox.com>
>To: dhcp-users at isc.org
>
>I am running server 3.0.1. I have a conf file that looks something like:
>
>option domain-name-servers 1.1.1.1 2.2.2.2 3.3.3.3;
>subnet 10.0.0.0 netmask 255.255.255.0 {
>    host xp-laptop {
>       hardware ethernet 00:aa:aa:bb:bb:bb;
>       fixed-address 10.0.0.123;
>       option domain-name-servers 10.0.0.1 10.0.0.2;
>    }
>}
>
>
>etc...
>The client (XP Pro) does a request and gets the correct information 
>(i.e. ip=10.0.0.123 and name server 10.0.0.1,10.0.0.2). However, about 2 
>minutes later, XP sends an "INFORM" packet. The server responds with the 
>correct IP (.123), but with the "global" name servers 1.1.1.1, 2.2.2.2, 
>3.3.3.3.
>
>If the client does a release and renew everything is fine, but it looks 
>like every INFORM request is answered only partially correct. (I.e. the 
>correct IP is returned, but the other options set in the host block are 
>ignored.)
>
>Has anyone seen this before?
>
>TIA!
>Craig
>
>P.S. I have a tcpdump showing the original "REQUEST" and the subsequent 
>INFORMs and ACKs.

Ok, what is happenning is that when a renew takes place, ie a
DHCPDISCOVER or DHCPREQUEST, the response gets the values
assigned with the host, in this case in the host statement. When
it does a DHCPINFORM it gets the values assigend in the subnet
scope, in this case this inherits form the global scope.

By the way, host statements are global in scope, so putting them
inside the subnet declaration does not tie them to that subnet.
Perhaps writing it like this would work better for you:

option domain-name-servers 1.1.1.1 2.2.2.2 3.3.3.3;
subnet 10.0.0.0 netmask 255.255.255.0 {
       option domain-name-servers 10.0.0.1 10.0.0.2;
}

host xp-laptop {
   hardware ethernet 00:aa:aa:bb:bb:bb;
   fixed-address 10.0.0.123;
}

The host entry will still inherit values fom the subnet
declaration due to the fact that the ip-address is from that
subnet. It might make it easier if you imagine there was several
subnets, and your laptop had several fixed addresses that
corresponded to the different subnets.

Secondly 3.0.1 is afew years old now, if possible yo should
consider upgrading as there have been a lot of fixes fom 3.0.1
to the current release 3.0.5.

regards,
-glenn