Newbie :DHCP server setup?

Umanga · 02-23-2010, 12:24 AM

greetings friends,

I am new to linux administration and I want to setup a DHCP server in my Debian server.

This server has a global IP (61.108.45.101 ) and my dhcpd.conf is configured as follows:

Code:

ddns-update-style none;
option domain-name "example.org";
option domain-name-servers ns1.example.org, ns2.example.org;
default-lease-time 600;
max-lease-time 7200;

authoritative;

subnet 192.0.0.0 netmask 255.255.255.0 {
  range 192.0.0.1 192.0.0.254;
  option routers rtr-239-0-1.example.org, rtr-239-0-2.example.org;
}

when I ran the 'dhcp' server it fails and the error in log is:

Quote:

Feb 23 15:22:23 biggjapan01 dhcpd: No subnet declaration for eth0 (61.108.45.101).
Feb 23 15:22:23 biggjapan01 dhcpd: ** Ignoring requests on eth0. If this is not what
Feb 23 15:22:23 biggjapan01 dhcpd: you want, please write a subnet declaration
Feb 23 15:22:23 biggjapan01 dhcpd: in your dhcpd.conf file for the network segment
Feb 23 15:22:23 biggjapan01 dhcpd: to which interface eth0 is attached. **
Feb 23 15:22:23 biggjapan01 dhcpd:
Feb 23 15:22:23 biggjapan01 dhcpd:
Feb 23 15:22:23 biggjapan01 dhcpd: Not configured to listen on any interfaces!

How can I configure DHCP for my lan ? I want the IP ranges 192.168.XXX.XXX ?

thanks in advance.

Lexus45 · 02-23-2010, 03:02 AM

First of all, you've written that you want to give 192.168.x.x addresses to your clients. But why do you have a strange subnet 192.0.0.0 netmask 255.255.255.0 parameter? You must write something like subnet 192.168.20.0 netmask 255.255.255.0 instead.

You may read this article to find some necessary parameters like INTERFACES="ethX" to understand, from what interface your computer must give the addresses to the local network.

And I insist on reading articles about private networks addressing

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)

http://en.wikipedia.org/wiki/Private_network
http://tools.ietf.org/html/rfc1918

Umanga · 02-24-2010, 12:12 AM

Thanks for the tips Lexus45,

But my server has only one networkcard.
Can I use single network card to connect the server to internet using global IP (eg: 61.203.12.32) and use as DHCP server which serve local IP ranges (192.168.XX.XX) ??

thanks

Quote:

Originally Posted by Lexus45

First of all, you've written that you want to give 192.168.x.x addresses to your clients. But why do you have a strange subnet 192.0.0.0 netmask 255.255.255.0 parameter? You must write something like subnet 192.168.20.0 netmask 255.255.255.0 instead.

You may read this article to find some necessary parameters like INTERFACES="ethX" to understand, from what interface your computer must give the addresses to the local network.

And I insist on reading articles about private networks addressing

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)

http://en.wikipedia.org/wiki/Private_network
http://tools.ietf.org/html/rfc1918

jlinkels · 02-24-2010, 02:50 AM

You cannot configure a DHCP server for a subnet which is not on one of your NIC's.

The IP address you mention (61.108.45.101) is a public IP address. I can't imagine that you want to give out addresses for that subnet, do you?

So you want to use 192.168.n.n on your local LAN, and your local LAN should pass thru this server to get to the Internet?

It can be done with just one network card if you give the card a second address:

Code:

ifconfig eth0:1 192.168.20.10 up

But then you'd still need a NAT router like iptables to route traffic from your local LAN to the internet.

Something like shorewall would do: http://www.shorewall.net/

Generally is it considered unsafe practice to have both internal and external network on just one interface they way I describe it. Invest the equivalent of US$ 19 for a second NIC. Give it the address 192.168.20.10. You DHCP server will work and you can route traffice to the internet trhu this box.

jlinkels