Overview
This document will show you how to configure a DHCP server listening to multiple VLANs. However, Abiquo recommends that you use a DHCP relay server to provide VLAN configuration.
A DHCP server only allows 200 VLANs. If more VLANs are needed, you should set up a DHCP relay server.
Abiquo recommends that you always use a DHCP relay server to provide VLAN support because it is difficult to scale this DHCP Server-only Configuration.
Install needed packages
You need to install vconfig (this is used to create VLANs), which is available in the EPEL repository:
# yum install epel-release && yum makecache && yum clean all # yum install vconfig
Create configuration scripts
To generate needed files, we will use Abiquo dhcpd config script.
# ./abiquo-dhcpd-config.py -h Usage: abiquo-dhcpd-config.py [OPTIONS]... Creates configuration files and start scripts for the DHCP server and VLANs. -h --help This help screen. -s --service-interface=INTERFACE Interface of the relay server connected to service network, where VLANs will be created. -v --vlan-range=VLANRANGE VLAN range (e.g. 2-200). -n --service-network=IP Network available for relay service interfaces (has to finish in 0).
It will generate 1 bash script (vlans-config) and 1 config file for DHCP server (/etc/sysconfig/dhcpd). For example:
DHCP server is connected to VLANs through eth1 (service network) DHCP server listens to VLAN range 2-200 Network for service network interfaces: 10.0.0.0
The service network is used to identify each VLAN interface. This network has to be different from every other network that the DHCP server has access to.
# ./abiquo-dhcpd-config.py -s eth1 -v 2-200 -n 10.0.0.0 -- Generating file -- * vlans-config Script to generate VLANs and assign IPs * dhcpd Script to configure dhcpd listen interfaces -- End --
Configure DHCP server
Ensure that the vlans-config service always starts before the dhcpd service.
VLANs init script
# cp vlans-config /etc/init.d/ # chkconfig vlans-config on # service vlans-config start
DHCP server
# cp dhcpd /etc/sysconfig/dhcpd # service dhcpd restart
Add a single out-of-range VLAN tag
To create a single out-of-range VLAN tag e.g. a new public VLAN, edit your script at /etc/init.d/vlan-config and look for text like this:
start() {
echo -n $"Starting $prog: "
for i in `seq 1 199`; do
vlan=$[0 + $i - 1 + 2]
vconfig add eth0 $vlan
ifconfig eth0.$vlan up
ifconfig eth0.$vlan 10.0.0.$i netmask 255.255.255.255
done
}
In the above example, we can see that the service interface is eth0, the range is 2-200 and the service IP is 10.0.0.0.
Following the example, if we want to add the VLAN Tag 500, we will add these lines:
vconfig add eth0 500 ifconfig eth0.500 up ifconfig eth0.500 10.0.1.2 netmask 255.255.255.255
The result will look like this:
start() {
echo -n $"Starting $prog: "
for i in `seq 1 199`; do
vlan=$[0 + $i - 1 + 2]
vconfig add eth0 $vlan
ifconfig eth0.$vlan up
ifconfig eth0.$vlan 10.0.0.$i netmask 255.255.255.255
done
vconfig add eth0 500
ifconfig eth0.500 up
ifconfig eth0.500 10.0.1.2 netmask 255.255.255.255
}
Now we will add the reverse command to stop the network. Look for text like this:
stop() {
echo -n $"Stopping $prog: "
killproc vlans-config
for i in `seq 2 200`; do
vconfig rem eth0.$i
done
RETVAL=$?
echo
return $RETVAL
}
And add these lines following the above example:
vconfig rem eth0.500
The result will look like this:
stop() {
echo -n $"Stopping $prog: "
killproc vlans-config
for i in `seq 2 200`; do
vconfig rem eth0.$i
done
vconfig rem eth0.500
RETVAL=$?
echo
return $RETVAL
}
Afterwards, save the file and restart the script. Now you need to add the VLAN you will be using to /etc/sysconfig/dhcpd:
Add it between the quotation marks to the end of any existing DHCPDARGS value (represented here as [...]):
DHCPDARGS="[...]"
Following the example above:
DHCPDARGS="[...] eth0.500"