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How to Install DHCP Server on CentOS 6

About DHCP

DHCP stands for Dynamic Host Configuration Protocol. This is a standardized network protocol and is used to automatically assign IP Address to computers on network. It is configured in a server-client model. DHCP server is the one assigning IP Addresses to client computers on the network. Each client is assigned a unique IP Address. DHCP server has a number of IP Addresses available in it’s pool. When all IP Addresses are taken, clients do not get any more IP Addresses.

DHCP client/server model

Install DHCP Server on CentOS
Install DHCP Server on CentOS

BEST PRACTICE:

DHCP FAILOVER:

This post does not cover DHCP server failover configuration. However DHCP failover is supported by ISC DHCP. The failover protocol only supports two DHCP servers and no more. Both DHCP servers share common address pool and each DHCP server has about half of the available IP addresses in the pool. I decided not to write about this DHCP failover solution – i might someday write a post how to install DHCP in afailover solution with Corosync and Pacemaker Linux Cluster!

Let’s Install DHCP Server on CentOS!

1. Install DHCP server packages

/usr/bin/yum install dhcp -y

2. Edit /etc/sysconfig/dhcpd file

Edit /etc/sysconfig/dhcpd file and enter the interface you want your DHCP server to run on.

[root@foo1 ~]# cat /etc/sysconfig/dhcpd
# Command line options here
DHCPDARGS=eth0

3. Copy dhcpd.conf sample to /etc/dhcpd/dhcpd.conf

Dhcpd.conf sample file

[root@foo1 ~]# cp /usr/share/doc/dhcp-4.1.1/dhcpd.conf.sample /etc/dhcp/dhcpd.conf

4. Edit dhcpd.conf file

Edit the /etc/dhcpd/dhcpd.conf file to reflect your desired configuration.

# dhcpd.conf
#
# Sample configuration file for ISC dhcpd
#

# option definitions common to all supported networks...
option domain-name "geekpeek.net";                                       # Change with your DomainName
option domain-name-servers 192.168.1.5, 192.168.1.6;                     # Change with your DNS IP Addresses or FQDN

default-lease-time 600;                                                  # Change with the desired lease time
max-lease-time 7200;                                                     # Change with the maximum desired lease time

# Use this to enble / disable dynamic dns updates globally.
#ddns-update-style none;

# 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;                                                     # Option to enable logging to /var/log/messages

# No service will be given on this subnet, but declaring it helps the 
# DHCP server to understand the network topology.

#subnet 10.152.187.0 netmask 255.255.255.0 {
#}

# This is a very basic subnet declaration.

subnet 192.168.1.0 netmask 255.255.255.0 {                               # Change with your network IP and Netmask
  range 192.168.1.10 192.168.1.250;                                      # IP Range to serve - our case from 192.168.1.10 to 192.168.1.250
  option routers 192.168.1.1;                                            # Change with IP Address of Gateway
}

# This declaration allows BOOTP clients to get dynamic addresses,
# which we don't really recommend.

#subnet 10.254.239.32 netmask 255.255.255.224 {
#  range dynamic-bootp 10.254.239.40 10.254.239.60;
#  option broadcast-address 10.254.239.31;
#  option routers rtr-239-32-1.example.org;
#}

# A slightly different configuration for an internal subnet.
#subnet 10.5.5.0 netmask 255.255.255.224 {
#  range 10.5.5.26 10.5.5.30;
#  option domain-name-servers ns1.internal.example.org;
#  option domain-name "internal.example.org";
#  option routers 10.5.5.1;
#  option broadcast-address 10.5.5.31;
#  default-lease-time 600;
#  max-lease-time 7200;
#}

# Hosts which require special configuration options can be listed in
# host statements.   If no address is specified, the address will be
# allocated dynamically (if possible), but the host-specific information
# will still come from the host declaration.

#host passacaglia {
#  hardware ethernet 0:0:c0:5d:bd:95;
#  filename "vmunix.passacaglia";
#  server-name "toccata.fugue.com";
#}

# Fixed IP addresses can also be specified for hosts.   These addresses
# should not also be listed as being available for dynamic assignment.
# Hosts for which fixed IP addresses have been specified can boot using
# BOOTP or DHCP.   Hosts for which no fixed address is specified can only
# be booted with DHCP, unless there is an address range on the subnet
# to which a BOOTP client is connected which has the dynamic-bootp flag
# set.

host foo2 {                                                              # Change with Hostname of host to assign fixed IP Address
  hardware ethernet 08:00:27:6B:06:7E;                                   # Change with fixed IP host MAC Address
  fixed-address 192.168.1.6;                                             # Change with the desired IP Address you want to assign to host
}

# You can declare a class of clients and then do address allocation
# based on that.   The example below shows a case where all clients
# in a certain class get addresses on the 10.17.224/24 subnet, and all
# other clients get addresses on the 10.0.29/24 subnet.

#class "foo" {
#  match if substring (option vendor-class-identifier, 0, 4) = "SUNW";
#}

#shared-network 224-29 {
#  subnet 10.17.224.0 netmask 255.255.255.0 {
#    option routers rtr-224.example.org;
#  }
#  subnet 10.0.29.0 netmask 255.255.255.0 {
#    option routers rtr-29.example.org;
#  }
#  pool {
#    allow members of "foo";
#    range 10.17.224.10 10.17.224.250;
#  }
#  pool {
#    deny members of "foo";
#    range 10.0.29.10 10.0.29.230;
#  }
#}

5. Start dhcpd service

[root@foo1 ~]# /etc/init.d/dhcpd start
Starting dhcpd:                                            [  OK  ]

6. Test DHCP server

You can test your DHCP server with a test DHCP client. Configure network on test DHCP client to check network for DHCP server. When DHCP server finds the DHCP client and assigns him an IP address you should see something like this in /var/log/messaged on the DHCP server:

....Dec 18 13:24:49 foo1 dhcpd: DHCPDISCOVER from 08:00:27:6b:06:7e via eth0
Dec 18 13:24:49 foo1 dhcpd: DHCPOFFER on 192.168.1.6 to 08:00:27:6b:06:7e via eth0
Dec 18 13:24:49 foo1 dhcpd: DHCPREQUEST for 192.168.1.6 (192.168.1.5) from 08:00:27:6b:06:7e via eth0
Dec 18 13:24:49 foo1 dhcpd: DHCPACK on 192.168.1.6 to 08:00:27:6b:06:7e via eth0
....

We can see DHCP client  (MAC 08:00:27:6b:06:7e) was offered and assigned IP address 192.168.1.6.

If you have any problems with starting DHCP service take a look at /var/log/messages for errors!

This is the end of “How to Install DHCP Server on CentOS 6” post. As said, i will write a post on How to install DHCP Server in Linux Cluster environment with Corosync and Pacemaker. Stay tuned!

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    • Alf

      Hi i like your job, thanks to this I understand somethings. Thank you
      I have a question, how can I get the address to my hardware ethernet?
      In your example it’s: hardware ethernet 08:00:27:6B:06:7E;
      but I don’t know how to get it

      • Mitch

        Hi Alf! You should be able to get the ethernet HW address using ifconfig command. Regards, Mitch

  • Mina

    Hi
    i followed these steps but am having a problem.
    the problem is that the dhcp server is not assigning the dns ip to the clients
    this is my dhcpd.conf file:

    ddns-update-style interim;
    subnet 10.0.0.0 netmask 255.0.0.0 {
    default-lease-time 600;
    max-lease-time 7200;
    option-domain-servers 8.8.8.8;
    range 10.0.0.20 10.0.0.254;
    option-routers 10.0.0.2;
    }

    example client ip values:
    IP : 10.0.0.200
    Broadcast ip : 10.255.255.255
    NetMask : 255.0.0.0
    GateWay : 10.0.0.2

    there is no dns server ip assigned

    • Mitch

      Hi Mina. Looking at your conf file i think you should fix the syntax when assigning option domain servers -> “option domain-name-servers 8.8.8.8;”. Hope this works out for you! Regards, Mitch

      • MIKE

        not at all

        • Mitch

          Please explain. Regards, Mitch

    • Mar1

      8.8.8.8 :
      this is public dns not internal one

  • John

    Hello I followed the instructions and even used the install script provided.
    In the end I got dhcpd to run but when I start another pc it does not get the ip assigned by my dhcp server.
    I am new to this and learning how to install a dhcp server that works for a school assignment.
    If anyone can help I will be so grateful because I am running out of time to finish this assignment and I really don’t get why it is not working.
    Here is my dhcp.conf:
    # /etc/dhcp/dhcpd.conf created by GeekPeek.Net scripts
    # Check /usr/share/doc/dhcp*/dhcpd.conf.sample for additional configuration parameters!

    # option definitions common to all supported networks…
    option domain-name “centos.local”;
    option domain-name-servers 8.8.8.8, 192.168.1.1;
    default-lease-time 600;
    max-lease-time 7200;

    # 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;

    # This is a very basic subnet declaration.
    subnet 192.168.219.0 netmask 255.255.255.0 {
    range 192.168.219.150 192.168.219.200;
    option routers 192.168.219.2;
    }

    I only have one CentOS 6.5 server running and one windows 7 pc running both I made with Vmware player and they both get use the Nat option on the network card in Vmware player.

    My CentOS 6.5 server has the following ip : 192.168.219.143
    And my win 7 : 192.168.219.144
    I am running both on my laptop.
    Here is the ifconfig on my CentoOS server:
    [root@localhost centos]# ifconfig
    eth0 Link encap:Ethernet HWaddr 00:0C:29:43:6A:38
    inet addr:192.168.219.143 Bcast:192.168.219.255 Mask:255.255.255.0
    inet6 addr: fe80::20c:29ff:fe43:6a38/64 Scope:Link
    UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
    RX packets:481 errors:0 dropped:0 overruns:0 frame:0
    TX packets:358 errors:0 dropped:0 overruns:0 carrier:0
    collisions:0 txqueuelen:1000
    RX bytes:137335 (134.1 KiB) TX bytes:31845 (31.0 KiB)
    Interrupt:19 Base address:0x2000

    lo Link encap:Local Loopback
    inet addr:127.0.0.1 Mask:255.0.0.0
    inet6 addr: ::1/128 Scope:Host
    UP LOOPBACK RUNNING MTU:16436 Metric:1
    RX packets:67 errors:0 dropped:0 overruns:0 frame:0
    TX packets:67 errors:0 dropped:0 overruns:0 carrier:0
    collisions:0 txqueuelen:0
    RX bytes:3510 (3.4 KiB) TX bytes:3510 (3.4 KiB)
    Here is the route command :
    [root@localhost centos]# route
    Kernel IP routing table
    Destination Gateway Genmask Flags Metric Ref Use Iface
    192.168.219.0 * 255.255.255.0 U 1 0 0 eth0
    default 192.168.219.2 0.0.0.0 UG 0 0 0 eth0

    here is the dhclient.leases :
    [root@localhost centos]# cat /var/lib/dhclient/dhclient.leases
    lease {
    interface “eth0”;
    fixed-address 192.168.219.143;
    option subnet-mask 255.255.255.0;
    option routers 192.168.219.2;
    option dhcp-lease-time 1800;
    option dhcp-message-type 5;
    option domain-name-servers 192.168.219.2;
    option dhcp-server-identifier 192.168.219.254;
    option broadcast-address 192.168.219.255;
    option domain-name “localdomain”;
    renew 2 2014/04/29 11:41:48;
    rebind 2 2014/04/29 11:54:38;
    expire 2 2014/04/29 11:58:23;
    }
    Please help me understand why it is not assigning the dynamic ip to the win 7 that is within my range of
    range 192.168.219.150 192.168.219.200 but instead it gives it 192.168.219.144.
    I tried to used also other ip schemes such as 192.168.0.0 255.255.2550
    But then the dhcpd would fail with the following error :
    Apr 30 02:51:45 localhost dhcpd: No subnet declaration for eth0 (192.168.219.143).
    Apr 30 02:51:45 localhost dhcpd: ** Ignoring requests on eth0. If this is not what
    Apr 30 02:51:45 localhost dhcpd: you want, please write a subnet declaration
    Apr 30 02:51:45 localhost dhcpd: in your dhcpd.conf file for the network segment
    Apr 30 02:51:45 localhost dhcpd: to which interface eth0 is attached. **
    Not configured to listen on any interfaces!

    Hopefully someone can find out where I went wrong and point me in the right direction to get this working.
    Yours sincerely John.

  • John

    Sorry my email was wrong in the first post if you are going to mail me please use this one.

  • shaik munaf

    Hi,
    I have gone through your procedure but i was not able to start dhcpd.
    error listed as

    Internet Systems Consortium DHCP Server 4.1.1-P1
    May 31 12:27:33 sam dhcpd: Copyright 2004-2010 Internet Systems Consortium.
    May 31 12:27:33 sam dhcpd: All rights reserved.
    May 31 12:27:33 sam dhcpd: For info, please visit https://www.isc.org/software/dhcp/
    May 31 12:27:33 sam dhcpd: Warning: subnet 192.168.146.0/24 overlaps subnet 192.168.146.0/24
    May 31 12:27:33 sam dhcpd: /etc/dhcp/dhcpd.conf line 35: expecting a declaration
    May 31 12:27:33 sam dhcpd: # option routers rtr-239-32-1.example.org;
    May 31 12:27:33 sam dhcpd: ^
    May 31 12:27:33 sam dhcpd: /etc/dhcp/dhcpd.conf line 44: expecting a declaration
    May 31 12:27:33 sam dhcpd: # max-lease-time 7200;
    May 31 12:27:33 sam dhcpd: ^
    May 31 12:27:33 sam dhcpd: /etc/dhcp/dhcpd.conf line 55: expecting a declaration
    May 31 12:27:33 sam dhcpd: # server-name “toccata.fugue.com”;
    May 31 12:27:33 sam dhcpd: ^
    May 31 12:27:33 sam dhcpd: Configuration file errors encountered — exiting
    May 31 12:27:33 sam dhcpd:
    May 31 12:27:33 sam dhcpd: This version of ISC DHCP is based on the release available
    May 31 12:27:33 sam dhcpd: on http://ftp.isc.org. Features have been added and other changes
    May 31 12:27:33 sam dhcpd: have been made to the base software release in order to make
    May 31 12:27:33 sam dhcpd: it work better with this distribution.
    May 31 12:27:33 sam dhcpd:
    May 31 12:27:33 sam dhcpd: Please report for this software via the CentOS Bugs Database:
    May 31 12:27:33 sam dhcpd: http://bugs.centos.org/
    May 31 12:27:33 sam dhcpd:
    May 31 12:27:33 sam dhcpd: exiting.

    can you plz provide me the soution for this as soon as possible.
    THanks alot.

    • Mitch

      Hi shaik, i will try to provide you with the solution asap. Regards, Mitch

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