Solved: Re: DHCP configuration

[David Shifflett <shifflett_(_at_)_nps_(_dot_)_navy_(_dot_)_mil>]

I have solved my problem.
I had to change the conf to define a 'shared network' as follows:
shared-network DEMO {
   subnet 192.168.0.0 netmask 255.255.255.0 {
       option routers 192.168.0.1;
   }
   subnet 192.168.1.0 netmask 255.255.255.0 {
       option routers 192.168.1.1;
   }
}

The relay agent had to be configured to set the gateway field
to its IP on the same subnet as the DHCP server
(in my example that would be 192.168.0.31)
This behavior is documented in RFC 2131
but is contrary to what is specified in RFC 1542 (section 4.1.1)

Thanks for all your help.
David Shifflett

David Shifflett wrote:

> Well I have a little more info:
> the line: dhcpd: DHCPOFFER on 192.168.1.100 to 00:10:5a:5d:73:0d via 
> 192.168.1.100
> is wrong, it is printing bogus info.
> The code uses inet_ntoa() to print the last field the gateway addr field.
> It also uses piaddr(), which also uses inet_ntoa()
> to print the first IP address, the leased address.
> These two calls to inet_ntoa() step all over each other,
> the first one is basically overwritten by the second.
>
> So that's a little debugging bug.
>
> Now the real problem:
> The server is trying to send the OFFER to 192.168.1.1 (the gateway),
> which it can't because it doesn't know about that subnet.
> So is the relay agent protocol broken?
> Should the relay agent specifiy his IP on the subnet of the server
> in the gateway field? (that would be 192.168.0.31 in my example)
>
> thanks for keeping me from pulling out all my hair
> David Shifflett
>
> David Shifflett wrote:
>
> > I need some help with a DHCP configuration.
> > I am trying to use OBSD 3.1 as my DHCP server
> > and I have a relay agent in the network.
> >
> > The request gets through and looks OK (please correct me if I'm wrong)
> > and the offer is prepared, but is sent back to the client (who doesn't
> > know his IP yet) and is on a different subnet.
> >
> > I expected that the offer would have been sent back to .0.31
> > to be relayed to the client.
> >
> > I have a relay between my client and the DHCP server as pictured below:
> >
> > server                      relay agent                     client
> > 192.168.0.25   -----  192.168.0.31 and 192.168.1.1   -----  x.x.x.x
> >
> > The log on the server shows:
> > dhcpd: DHCPDISCOVER from 00:10:5a:5d:73:0d via 192.168.1.1
> > dhcpd: DHCPOFFER on 192.168.1.100 to 00:10:5a:5d:73:0d via 192.168.1.100
> >
> > I tried configuring the relay agent to send 192.168.0.31
> > in the gateway addr field and got:
> > DHCPDISCOVER from 00:10:5a:5d:73:0d via 192.168.0.31
> > no free leases on subnet 192.168.0.0
> >
> >
> > The dhcpd.conf file read as follows (names have been sanitized):
> > default-lease-time 600;
> > max-lease-time 7200;
> > option subnet-mask 255.255.255.0;
> > option broadcast-address 192.168.0.255;
> > option domain-name-servers 192.168.0.25;
> > option domain-name "MY DOMAIN";
> > allow bootp;
> > deny unknown-clients;
> > subnet 192.168.0.0 netmask 255.255.255.0 {
> >     option routers 192.168.0.31;
> > }
> > subnet 192.168.1.0 netmask 255.255.255.0 {
> >     option routers 192.168.0.31;
> > }
> > group {
> >     default-lease-time -1;
> >     server-name "SERVER.MY DOMAIN";
> >     server-identifier 192.168.0.25;
> >     use-host-decl-names on;
> >     host CLIENT {
> >         hardware ethernet 00:10:5A:5D:73:0D;
> >         fixed-address 192.168.1.100;
> >         filename "/CLIENT/zImage";
> >     }
> > }
> >
> >
> > thanks for any help
> > David Shifflett