[TriLUG] DHCPD and multiple NICs

[Tom Bryan]

Now that I have RoadRunner (Yeah!), my DHCP server for my home network is 
also the firewall/gateway to the public network.  (It's also my NFS server, 
but that's another question.)  I configured eth1 and plugged it into the 
cable modem, but I had problems with the machine's own DHCPD fighting with 
the cable modem's DHCP server.  From an old message on the list, I set added 
an extra subnet block to dhcpd.conf.  I'm not really sure what this does.  
Everything seems to work now, but DHCPD is still listening on eth0 and eth1.

subnet 0.0.0.0 netmask 0.0.0.0 {
        not authoritative;
}
 
subnet 172.16.0.0 netmask 255.255.255.0 {
        host ....
}

Can anyone explain the first subnet block to me?  Is it a just a hack, or is 
this the right way to do it?  The reason I ask is that whenever I boot, I get

Sep 15 07:50:27 dhcpd: Warning: subnet 172.16.0.0/24 conflicts 
with subnet 0.0.0.0/0
Sep 15 07:50:27 dhcpd: Listening on Socket/eth1/0.0.0.0
Sep 15 07:50:27 dhcpd: Sending on   Socket/eth1/0.0.0.0
Sep 15 07:50:27 dhcpd: Listening on Socket/eth1/0.0.0.0
Sep 15 07:50:27 dhcpd: Sending on   Socket/eth1/0.0.0.0
Sep 15 07:50:28 dhcpd: Listening on Socket/eth0/172.16.0.0
Sep 15 07:50:28 dhcpd: Sending on   Socket/eth0/172.16.0.0
Sep 15 07:50:28 dhcpd: Listening on Socket/eth0/172.16.0.0
Sep 15 07:50:28 dhcpd: Sending on   Socket/eth0/172.16.0.0
Sep 15 07:50:28 dhcpd: dhcpd startup succeeded

---Tom