I have a piece of wire (thinnet) with 3 computers. What I am trying to do is
have 2 of them on different networks eg., A on 192.168.0.0/24 and B on
192.168.1.0/24, and the third, tape2, on 192.168.0.0/23 ie. both? 

According to man dhcpd:

Subnets
       dhcpd needs to know the subnet numbers and netmasks of all
       subnets for which it will be providing service.

I was hoping to be able to generate a dhcpd.conf file with

subnet 192.168.0.0 netmask 255.255.255.0 { machine A fixed addr definition }
subnet 192.168.1.0 netmask 255.255.255.0 { machine B fixed addr definition }

A works fine, but when B tries to query dhcp:

Dec  3 12:22:37 tape2 dhcpd: DHCPDISCOVER from 00:00:b4:84:13:49 via ne1
Dec  3 12:22:37 tape2 dhcpd: no free leases on subnet 192.168.0.0

Now, agreed B's definition is not in 192.168.0.0/24, but why isn't the
192.168.1.0/24 searched?

Dec  3 12:22:05 tape2 dhcpd: Listening on BPF/ne1/00:20:a9:0a:e4:e2/192.168.0.0
Dec  3 12:22:05 tape2 dhcpd: Sending on   BPF/ne1/00:20:a9:0a:e4:e2/192.168.0.0

I presume this means 192.168.0.0/23 rather than /24, as that is what ne1 is
set to..

Any thoughts?

Cheers,

Patrick
PS server tape2 is NetBSD-1.4L/i386, clients are NetBSD-1.4K/i386