Implementation of DHCP

Implementation of DHCP 

The Dynamic Host Configuration Protocol (DHCP) is a network management protocol used on UDP/IP networks whereby a DHCP server dynamically assigns an IP address and other network configuration parameters to each device on a network so they can communicate with other IP networks.

To configure dynamic IP address assignment on multiple VLAN with a unique DHCP server appliance on the network.

Two VLANs are configured on Switch0 with Router0 as default gateway :

• VLAN 10 - Nework : 192.168.10.0/24 - Gateway : 192.168.10.1 (FA 0/0.10)
• VLAN 20 - Network : 192.168.20.0/24 - Gateway : 192.168.20.1 (FA 0/0.20)

The unique DHCP server is located on a remote subnet with IP 172.16.24.2.

DHCP configuration

Declare IP address pools on the DHCP management tab of the server like on the picture below. One pool has to be declared for each VLAN. Don't forget to configure the right network settings and default gateway (Router0 FA 0/0.10 and FA 0.0.20 IP address) for each VLAN.

Configure router0 for DHCP forwarding to the DHCP server (DHCP relay)

Router(config)# interface FastEthernet0/0.10

Router(config-subif)# encapsulation dot1Q 10

Router(config-subif)# ip address 192.168.10.1 255.255.255.0

Router(config-subif)# ip helper-address 172.16.24.2

Router(config)# interface FastEthernet0/0.20

Router(config-subif)# encapsulation dot1Q 20

Router(config-subif)# ip address 192.168.20.1 255.255.255.0

Router(config-subif)# ip helper-address 172.16.24.2

Configure router0 for DHCP forwarding to the DHCP server (DHCP relay)

Router(config)# interface FastEthernet0/0.10

Router(config-subif)# encapsulation dot1Q 10

Router(config-subif)# ip address 192.168.10.1 255.255.255.0

Router(config-subif)# ip helper-address 172.16.24.2

Router(config)# interface FastEthernet0/0.20

Router(config-subif)# encapsulation dot1Q 20

Router(config-subif)# ip address 192.168.20.1 255.255.255.0

Router(config-subif)# ip helper-address 172.16.24.2