Sample Configurations

1. LAN machines are within the same subnet under a router using the same router as DHCP server

Assumptions
* The LAN subnet is 192.168.1.0/24
* There are no local DNS servers within the LAN, so external ISP-managed DNS servers of 4.2.2.5, 4.2.2.6, 4.2.2.66 IP addresses are used
* The router Ethernet0 interface that connects to the LAN is used as default gateway for all LAN machines, so the Ethernet0 interface IP address is set as default router (default gateway in DHCP terminology)
* You reserve IP address range of 192.168.1.1 to 192.168.1.30 for statically-assigned hosts within the LAN where the 192.168.1.1 is the router and 192.168.1.2 to 192.168.1.30 are the servers or any other network devices

ip dhcp excluded-address 192.168.1.1 192.168.1.30
!
ip dhcp pool insideDHCP
network 192.168.1.0 255.255.255.0
default-router 192.168.1.1
dns-server 4.2.2.5 4.2.2.6 4.2.2.66
!
interface Ethernet0
description Facing my LAN
ip address 192.168.1.1 255.255.255.0
 

2. LAN machines are within the same subnet under a ASA/PIX Firewall using the same firewall as DHCP server

Assumptions
* The LAN subnet is 10.0.0.0/24
* There are no local DNS servers within the LAN, so external ISP-managed DNS servers of 68.87.64.196 and 68.87.66.196 IP addresses are used
* The ASA/PIX Firewall inside interface that connects to the LAN is used as default gateway for all LAN machines, so the inside interface IP address is set as default gateway in for all LAN DHCP client machines, which is the 10.0.0.1
* You reserve IP address range of 10.0.0.1 to 10.0.0.29 for statically-assigned hosts within the LAN where the 10.0.0.1 is the ASA/PIX Firewall and 10.0.0.2 to 10.0.0.29 are the servers or any other network devices
* DHCP assigned IP address expires in 3600 seconds (1 hour). Typically ASA/PIX Firewall assign the same IP address to the same LAN machine (with the same MAC address) although it is possible to have different IP address for the LAN machine in question when the LAN machine's MAC address is already expired off MAC address table.

ip address inside 10.0.0.1 255.255.255.0
dhcpd address 10.0.0.30-10.0.0.254 inside
dhcpd dns 68.87.64.196 68.87.66.196
dhcpd lease 3600
dhcpd ping_timeout 750
dhcpd enable inside
 

3. LAN machines are within different subnet and VLAN under Layer-3 Switch using Windows 2003 server as dedicated DHCP server
»Single DHCP for multiple Vlans Design

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by aryoba
last modified: 2010-04-22 14:36:50