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Configuring DHCP Server

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By User

What is DHCP?

The DHCP (Dynamic Host Configuration Protocol) is an Internet protocol responsible for automating the configuration of computers which use TCP/IP. DHCP can be used to assign IP addresses to computers by delivering TCP/IP configuration addresses such as IP address, subnet masks, default routers and DNS addresses. It can also be used to provide information for a number of other services such as printers, time, news and TFTP servers.

Config

A Cisco router can be configured as a DHCP server to assign IP addresses. The range of IP addresses which can be given out is called a 'pool'. From this pool clients are leased addresses for a given time, after which the lease expires and the client needs to request a new IP address lease.
The following config lines show how to setup a DHCP pool of addresses in the 192.168.0.0 IP range:

no ip dhcp conflict logging
ip dhcp excluded-address 192.168.0.1 192.168.0.50
!
ip dhcp pool 1 
  network 192.168.0.0 255.255.255.0
  default-router 192.168.0.100
  domain-name jlsnet.co.uk
  dns-server 192.168.0.1 19 194.168.8.100
  next-server 192.168.0.1

The config above also shows how to set the Default Gateway and DNS Servers which are assigned to clients.
The Ethernet address of the switch is "00:07:eb:94:73:c0" and I wanted to assign a manual IP address 192.168.0.100 to it. So I declared:

ip dhcp pool switch
  host 192.168.0.99
  hardware-address 0007.eb94.73c0
  client-name switch
  default-router 192.168.0.100
  dns-server 192.168.0.1 194.168.8.100 194.168.4.100
  next-server 192.168.0.1

Afterwards, as I did a "show ip dhcp binding" on the router, I get the following results:
 
router1#sh ip dhcp binding

IP address       Client-ID/              Lease expiration        Type
                 Hardware address
192.168.0.51     0100.02b3.91f7.34       Apr 05 2003 06:14 AM    Automatic
192.168.0.53     0100.0423.468b.31       Apr 05 2003 08:42 AM    Automatic
192.168.0.69     0100.0423.4682.ab       Apr 05 2003 07:15 AM    Automatic
192.168.0.99     0007.eb94.73c0          Infinite                Manual
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