How to Setup a DHCP Server
on Red Hat/Centos 6.x
DHCP stands for (Host
Configuration Protocol). It is used to assign IP addresses automatically at
boot time to network clients.
There are basically two ways
of assigning IPs to Hosts or devices on any given network; manually or by using
an automated method (DHCP Server).
This is my opinion based on past experience.
I think if your network is
relatively small, between 10-50 hosts/devices, I would recommend using static
IPs instead of a DHCP server. There are pros and cons in doing so.
For example if you need
resiliency for your network you will need to start to think about redundancy
for your DHCP server. There are options, but things start to become unnecessary
complex. I know some sys admins; they use DHCP for everything, including
servers. I just think it is not a good idea.
Package requirement
·
dhcp.x86_64· dhcp-common.x86_64
Installing packages
[root@centos63 ~]# yum install
dhcp.x86_64 dhcp-common.x86_64 –y
Start-up DHCP service at boot time
[root@centos63 ~]# chkconfig --level 2345 dhcpd onUse the sample configuration to start with
[root@centos63 ~]# vi /etc/dhcp/dhcpd.conf
Note:
Copy and paste the lines below:
# Sample DHCP generated by Renato de Oliveira
# http://ukaying.blogspot.co.uk# option definitions (Domain Name)
option domain-name "adlinux.int";
# Lease time and expiration
default-lease-time 600;max-lease-time 7200;
# If this DHCP server is the official DHCP server for the local
# network, the authoritative directive should be uncommented.authoritative;
# Use this to send dhcp log messages to a different log file
(you also
# have to hack syslog.conf to complete the redirection).log-facility local7;
# DHCP netwok and mask decalaration
subnet 192.168.1.0 netmask 255.255.255.0 {range 192.168.1.100 192.168.1.160;
option routers 192.168.1.1;
option domain-name-servers "192.168.1.22";
option domain-name "adlinux.int";
}
# Fixed IP addresses can also be specified for hosts.
host linadws01 {hardware ethernet 00:0c:29:eb:dc:90;
fixed-address 192.168.1.160;
}
Note: Make
sure you change this file to suit your needs. For example, remember to change
Domain Name, IP Addresses, and Name Servers etc.
Start the DHCP Server Service
[root@centos63 ~]#
service dhcpd start
Note: If the service fails to start, check /var/log/messages, it will give you a very good idea on
what is wrong. Most the time it is syntax or typos.
Testing
On another Linux Server, change the
file /etc/sysconfig/network-scripts/ifcfg-eth0 to use DHCP, see below:
[root@centos63 ~]# vi /etc/sysconfig/network-scripts/ifcfg-eth0
DEVICE=”eth0”
BOOTPROTO=dhcpONBOOT=yes
Reboot
the Client
Watch the logs on the server
[root@centos63 ~]# tail –f /var/log/messages
You should see an
output similar to the one below:
Apr 14 17:26:44 centos63 dhcpd: DHCPDISCOVER from
00:0c:29:eb:dc:90 via eth0
Apr 14 17:26:44 centos63 dhcpd: DHCPOFFER on 192.168.1.160 to
00:0c:29:eb:dc:90 via eth0Apr 14 17:26:44 centos63 dhcpd: Dynamic and static leases present for 192.168.1.160.
Apr 14 17:26:44 centos63 dhcpd: Remove host declaration linadws01 or remove 192.168.1.160
Apr 14 17:26:44 centos63 dhcpd: from the dynamic address pool for 192.168.1.0/24
Apr 14 17:26:44 centos63 dhcpd: DHCPREQUEST for 192.168.1.160 (192.168.1.34) from 00:0c:29:eb:dc:90 via eth0
Apr 14 17:26:44 centos63 dhcpd: DHCPACK on 192.168.1.160 to 00:0c:29:eb:dc:90 via eth0
Still on the client, check:
[root@centos63 ~]# ifconfig
2. Check its default gateway
[root@centos63 ~]# route –n
3. Check the /etc/resolv.conf
[root@centos63 ~]#cat /etc/resolv.conf
; generated by /sbin/dhcpclient-script
search adlinux.int
nameserver 192.168.1.22
If you can
confirm the results above, then you have successfully setup a DHCP server for
your network. If you have problems, just keep an eye on /var/log/messages.
Hope you enjoyed
this post.
By Renato de
Oliveira
