Handling multiple subnets with DHCP/DNS

Kristijan · 03-17-2007, 12:28 AM

Hi All,

I have a NetBSD box at the moment currently set up with DHCP, DNS and PF. There are currently two NIC’s in the box – fxp0 & fxp1. The DHCP server also updates the DNS server with any new clients which obtain a new address.

At the moment, DHCP and DNS only look after a single address range – 192.168.0.0/24. All this works fine, but I’m now looking at incorporating in a wireless AP, but want to assign any wireless workstations address from the 192.168.1.0/24 subnet.

The NetBSD box will eventually have three NIC’s;

fxp0 192.168.0.0 – Internal LAN
fxp1 10.0.0.0 (ppp0 bridge) – Internet
fxp2 192.168.1.0 – Wireless LAN (Which my AP will plug into)

My question is do I simply just add another subnet declaration in /etc/dhcpd.conf like this?

Code:

 subnet 192.168.0.0 netmask 255.255.255.0 {
        do-forward-updates true;
        range 192.168.0.50 192.168.0.100;
        option subnet-mask 255.255.255.0;
        option domain-name-servers 192.168.0.10;
        option domain-name "in.kristijan.org";
        option routers 192.168.0.10;
}

subnet 192.168.1.0 netmask 255.255.255.0 {
        do-forward-updates true;
        range 192.168.1.1 192.168.1.25;
        option subnet-mask 255.255.255.0;
        option domain-name-servers 192.168.0.10;
        option domain-name "in.kristijan.org";
        option routers 192.168.0.10;
}

And another entry in the zone updates declaration?

Code:

 zone 0.168.192.in-addr.arpa. {
        primary 127.0.0.1;
        key rndc-key;
}

zone in.kristijan.org. {
        primary 127.0.0.1;
        key rndc-key; 

}

zone 1.168.192.in-addr.arpa. {
        primary 127.0.0.1;
        key rndc-key;
}

If that’s the case, how does DHCP know which address to assign which workstation? Example, if I plug a box into my switch, I’d expect an address from the 192.168.0.0 subnet, but if a wireless box connected via the AP, I’d expect an address from the 192.168.1.0 range.

Same question about the zone updates, how does DHCP know which zone file to update?

Hope this makes sense

Cheers,
-Kristijan

ARC1450 · 03-17-2007, 06:54 PM

You'd give your WAP a 192.168.1.0/24 address, and yes, DHCP should figure out the rest.

But DHCP would also assume that if an address is coming into it's 192.168.1.0/24 interface, it would need a 192.168.1.0/24 address. Else, how would it get to a gateway?

Kristijan · 03-17-2007, 07:57 PM

Hi ARC1450,

Thanks for the response. I'm just waiting on a 3rd NIC to come in so I can go and give this all a test run. I guess that the DHCP will be smart enough to update the correct DNS zone as well then.

Once it's all in and I've run through it a few times, I'll let you know how it all went

Cheers,
-Kristijan