dhcpd on two NICs

spitzwegerich · Posted: Fri Dec 26, 2003 12:32 pm Post subject: dhcpd on two NICs

Hello!

I want to set up a dhcp-server for a non-profite youth-organisation.

At the moment there are 3 network adapters in the server. One is for the connection to the internet, the others should form two independent local area networks. (One for office boxes, one for teaching purposes.)

Both networks should receive their IPs via DHCP from the server, and they should form different IP subnets (10.0.0.X and 10.0.1.X).
So the problem is to tell dhcpd to differentiate between the 2 network adapters and to assign IPs depending on that. For administration ease I do not want to maintain a MAC-database of the clients NICs.

I had a look to the manpages of dhcpd and dhcpd.conf, but I could not find any solution besides maybe running 2 dhcpds parallel (which does not look like a clean solution to me).

I would welcome any idea on the topic (configuring dhcpd or maybe change the complete setup).

Many thanks,

~michael
_________________
"Work is the curse of the drinking classes."
-Oskar Wilde

nasher · Tux's lil' helper Joined: 21 Feb 2003 Posts: 125

im not sure if this is what u mean but,

u've 2 nics

1st NET = 10.0.1.0
2nd NET = 10.0.2.0

in /etc/conf.d/dhcp u assign both adapters (eth0 / eth1) (or something).

then u eddit your dhcp.conf

(range dfgw ns etc)

i guess your network is something like this
the xxx are just for filling up ;o

xxxxxxxxxxxxxxxxxx/-- > <switch1> 10.0.1.0 > clients
internet eth -><- pc -
xxxxxxxxxxxxxxxxxx\-- > <switch2> 10.0.2.0 > clients

dhcp should auto assign ips to clients in the same net

i.e.,
when you hang a client in NET 10.0.1.0 he gets an ip between 10.0.1.2 10.0.1.254 (this is what u need to eddit in dhcp.conf)

---
its better to give your eth's nics ips like 10.0.1.1 and 10.0.2.1

and for clients, ranges between .50 / .200 or something

under .50 you can asssign other servers / printers and above .200(till 254) too . .

bokkepoot · Posted: Fri Dec 26, 2003 1:04 pm Post subject:

The following setup works for me with the same layout as you have: 1 nic for the world, 2 seperate local networks, and 1 dhcp running:

/etc/dhcp/dhcpd.conf

nasher · Tux's lil' helper Joined: 21 Feb 2003 Posts: 125

think4urs11 · Posted: Fri Dec 26, 2003 1:44 pm Post subject:

nasher · Tux's lil' helper Joined: 21 Feb 2003 Posts: 125

hm
what i've learned is

10.0.0.0 /8
172. /16
192 /24

ok i should have it wrong, but explain me why you can use subnetmasker like that

think4urs11 · Posted: Fri Dec 26, 2003 2:03 pm Post subject:

Mhhh...

what you mean (i think at least) is

10.0.0.0 - 10.255.255.255 (10/8 prefix)
172.16.0.0 - 172.31.255.255 (172.16/12 prefix)
192.168.0.0 - 192.168.255.255 (192.168/16 prefix)

That are the ip ranges meant for private use (RFC1918)

But nowadays it is no longer needed to use the old classful addressing scheme - meaning /8, /16, /24 dependand on the first/second octet.
At least if you don't have one of those strange boxes which still don't know about CIDR.

Today you can have subnet masks from /8 - /30 (/31) - it just depends on what you need. And (if you need offical ips) on what you can pay.

HTH
T.
_________________
Nothing is secure / Security is always a trade-off with usability / Do not assume anything / Trust no-one, nothing / Paranoia is your friend / Think for yourself

spitzwegerich · Posted: Fri Dec 26, 2003 4:18 pm Post subject:

thanks for your answers!

My problem was that I did not understand that the subnet sections are assigned to the NICs given to dhcpd on startup.
_________________
"Work is the curse of the drinking classes."
-Oskar Wilde

spitzwegerich · Posted: Fri Dec 26, 2003 7:54 pm Post subject:

@bokkepoot

I started from your dhcpd.conf and tried to understand it with the manpage of dhcpd.conf. I found this: