Tech: dhcpd tips, and how you should get it to work on a totally separate network

For the poor sods who had problems with dhcpd – my DHCP troubleshooting notes. Done on a Fedora box, version 10 IIRC.

Restart network interfaces:

service network restart

to use tcpdump for packet capture on the server:

tcpdump -i -n port 67 or port 68

run dhcpd in debug mode in foreground:

/usr/sbin/dhcpd eth1 -d -f

stop service:

/etc/rc.d/init.d/dhcpd stop

run dhcpd on eth1 specifically:

/usr/sbin/dhcpd eth1

If you are looking to run dhcpd as a server for other subnets, but not on the subnet it is on, the below sample /etc/dhcpd.conf shows the server as having a static IP address of, but it only acts as a DHCP server on the network

(I used Cisco’s ip-helper to relay the DHCP broadcasts across to network, if you were wondering.)

Credit to jmcdaniel for the configuration below.

ddns-update-style interim;
ignore client-updates;

#This is a filler to make dhcpd believe the adapter is valid
subnet netmask {

#This is the dhcpd configuration for the STB network
subnet netmask {
option broadcast-address;
option routers;
option subnet-mask;
# option domain-name "";
option domain-name-servers;
# IP address allocation range from to
range dynamic-bootp;
default-lease-time 21600;
max-lease-time 43200;