Network administrations

How to configure dhcp server in Linux

DHCP, or Dynamic Host Configuration Protocol, allows an administrator to configure network settings for all clients on a central server.

The DHCP clients request an IP address and other network settings from the DHCP server on the network. The DHCP server in turn leases the client an IP address within a given range or leases the client an IP address based on the MAC address of the client's network interface card (NIC). The information includes its IP address, along with the network's name server, gateway, and proxy addresses,including the netmask.

Nothing has to be configured manually on the local system, except to specify the DHCP server it should get its network configuration from. If an IP address is assigned according to the MAC address of the client's NIC, the same IP address can be leased to the client every time the client requests one. DHCP makes network administration easier and less prone to error.

Exam Question Configure the DHCP server by matching the following conditions:

  • Subnet and netmask should be 192.168.0.0 255.255.255.0
  • Gateway Should be 192.168.0.254
  • DNS Sever Should be 192.168.0.254
  • Domain Name should be example.com
  • Range from 192.168.0.10-50

Exam Question You have DHCP server, which assigns the IP, gateway and DNS server ip to Clients. There is one DNS servers having MAC address (00:50:FC:98:8D:00 in your LAN, But it always required fixed IP address (192.168.0.10). Configure the DHCP server to assign the fixed IP address to DNS server.

Configure dhcp server

In this example we will configure a dhcp server and will lease ip address to clients.

For this example we are using three systems one linux server one linux clients and one window clients.

dhcp rpm is required to configure dhcp server. check it if not found then install
rpm

Now check dhcpd service in system service it should be on

#setup
Select  System service
from list [*]dhcpd

To assign IP to dhcp server

DHCP server have a static a ip address. First configure the ip address 192.168.0.254 with netmask of 255.255.255.0 on server.

Run setup command form root user

 #setup 

setup

this will launch a new window select network configuration

network configurations

now a new window will show you all available LAN card select your LAN card ( if you don't see any LAN card here mean you don't have install driver)

select lan devices in setup

assign IP in this box and click ok

assign ip address

click on ok, quit and again quit to come back on root prompt.

restart the network service so new ip address can take place on LAN card

 #service network restart 

main configuration file of dhcp server is dhcpd.conf. This file located on /etc directory. If this file is not present there or you have corrupted this file, then copy new file first, if ask for overwrite press y

cp dhcpd sample file

now open /etc/dhcpd.conf
vi dhcpd
default entry in this file look like this
dhcpd.conf
make these change in this file to configure dhcp server

remove this line # - - - default gateway
set option routers to 192.168.0.254
set option subnet-mask to 255.255.255.0
option nis domain to example.com
option domain-name to example.com
option domain-name-servers to 192.168.0.254
range dynamic-bootp to 192.168.0.10 192.168.0.50;

After change this file should look like this
dhcpd.conf

how to assign fix ip address to any host

locate this paragraph and change hardware Ethernet to client's mac address and fixed -address to ip address which you want to provide that host
dhcpd.conf
after making necessary change save file and exit

now create a blank file use to store the allocated ip address information
touch

Now restart dhcpd service and on it with chkconfig commands

service dhcpd restart

Linux Client configuration

Client configuration is very easy and straightforward. All you need to do is set ip address to dynamic in the properties of lan card. In linux

#setup
select  network configuration from menu list
Select  lan card and enter on ok
Select  USE DHCP and enter on ok
Now click on  quit
and  quit to come back on root prompt

Now restart the network service to obtain ip from dhcp server

service network restart

Window Client configuration

To configure windows system as dhcp clients open lan card properties and select tcp/ip and click on properties and set obtain ip address automatically
lan card porperties

Go on command prompt and check new ip address
ipconfig

Check lease on DHCP server

you can check allocated address on server.
 cat
cat lease

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