To enable dhcp server for mutil-interface

Under Ubuntu 8.04.3

* get DHCP server
sudo apt-get install dhcp3-server

* enable networking interface for DHCP server
sudo vi /etc/default/dhcp3-server

# what interface provide DHCP service
INTERFACES="wlan0 eth1"

* edit the DHCP server parameter
sudo vi /etc/dhcp3/dhcpd.conf

ddns-update-style none;
log-facility local7;

subnet 192.168.5.0 netmask 255.255.255.0 {
option routers 192.168.5.1;
option subnet-mask 255.255.255.0;
option broadcast-address 192.168.5.255;
option domain-name-servers 172.16.100.1, 172.16.100.16;
# option ntp-servers 172.16.100.1;
# option netbios-name-servers 172.16.100.1;
option netbios-node-type 2;
default-lease-time 86400;
max-lease-time 86400;

range 192.168.5.21 192.168.5.30;
}


Reference:
https://help.ubuntu.com/community/dhcp3-server