DHCP Cisco IOS

Computer Networking articles. Contains articles not suitable for specific categories like Category:Cisco, Category:CCNA, Category:CCNP or Category:IOS

	The information in this article is targeted to Cisco CCNA and CCNP curriculum, and not meant as in-depth information on all IOS

DHCP Server

IOS DHCP Servers service is installed Cisco Router IOS and not on Cisco Switch IOS.

DHCP Server example with fixed options

! 
ip dhcp excluded-address 192.168.22.1 192.168.22.99
ip dhcp excluded-address 192.168.22.200 192.168.22.255
!
ip dhcp pool STUDENTS
  network 192.168.22.0 255.255.255.0
  domain-name tekkom.dk
  default-router 192.168.22.1
  dns-server 192.168.22.223 
!

DHCP Server often used SHOW commands

Show leased addresses

Mercantec#show ip dhcp binding
IP address       Client-ID/Hardware address	 	Lease expiration            Type
192.168.22.100   0063.5973.636f.9da6.                   Jan 25 2009 12:30 AM        Automatic
192.168.22.101   0063.6c72.636f.6e38.                   Jan 25 2009 12:53 AM        Automatic
192.168.22.108   0063.7e7a.636f.247f.                   Jan 25 2009 14:32 AM        Automatic

Show Server statistics

Mercantec#show ip dhcp server statistics
Memory usage         13906
Address pools        1
Database agents      1
Automatic bindings   1
Manual bindings      0
Expired bindings     0
Malformed messages   0

Message              Received
BOOTREQUEST          0
DHCPDISCOVER         1
DHCPREQUEST          1
DHCPDECLINE          0
DHCPRELEASE          0
DHCPINFORM           0

Message              Sent
BOOTREPLY            0
DHCPOFFER            1
DHCPACK              1
DHCPNAK              0

DHCP Client

DHCP Client simple example

interface FastEthernet0/1
  ip address dhcp

DHCP Client and Server with NAT/PAT example

ip dhcp excluded-address 192.168.22.1 192.168.22.99
ip dhcp excluded-address 192.168.22.200 192.168.22.255
!
ip dhcp pool HETH
   network 192.168.22.0 255.255.255.0
   domain-name tekkom.dk
   default-router 192.168.22.1
   dns-server 192.168.22.223
!
interface FastEthernet0/0
 description Inside. Internal LAN
 ip address 192.168.22.1 255.255.255.0
 ip nat inside
!
interface FastEthernet0/1
  description Outside: Internet connection to ISP
 ip address dhcp
 ip nat outside
!
ip nat inside source list 1 interface FastEthernet0/1 overload
!
access-list 1 permit 10.0.0.0 0.255.255.255
access-list 1 permit 172.16.0.0 0.15.255.255
access-list 1 permit 192.168.0.0 0.0.255.255

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