DHCP Configuration 3 Points

A number of Windows XP users on VLAN_D support DHCP and the ability to receive more than one IP gateway. Configure R2 to provide only a pool of DHCP addresses with the following criteria:

■ The IP addresses pool ranges from shared between R2 and R3.

■ The DNS servers are and

■ Default gateway of or only.

■ Hosts must retain DHCP-assigned addresses forever.

■ The predefined addresses,, and are never allocated to DHCP clients.

You can assume that you have Windows XP clients only and support more than one gateway if any one router fails.

DHCP Configuration Solution

VLAN_D contains the subnet with the allocated IP addresses, one each to R2 E0/0, R3 Fast0/0, and the Catalyst 3550 management interface. You must ensure that any DHCP servers (R2, in this case) do not allocate these three preassigned address.

Example 8-63 configures R2 for DHCP pool allocation.

Example 8-63 DHCP Configuration on R2

ip dhcp excluded-address ip dhcp excluded-address ip dhcp excluded-address !

ip dhcp pool ccie network

domain-name cisco.com dns-server

default-router lease infinite

R2 provides the DNS domain name and two default gateways. Notice that the lease is enabled to be used forever by DHCP clients with the IOS command lease infinite. If R2 fails, all DHCP clients with existing IP addresses will route through Router R3 with the default gateway

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