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How to configure the DHCP relay feature on the PIX firewall

Core issue

Configuration of DHCP feature on the Pix firewall.

Resolution

The Dynamic Host Configuration Protocol (DHCP) daemon must be enabled to listen for DHCP client requests.

When the PIX Firewall acts as a DHCP server, PIX provides network configuration parameters to DHCP clients.
Dynamically assigned IP addresses are an example for network configuration parameters. These configuration parameters provide a DHCP client with the networking parameters necessary to access an enterprise network and network services like the Domain Name System (DNS).

The DHCP server on PIX does not support failover. If a DHCP server runs on PIX, the MAC address-to-IP address bindings are not replicated to the secondary standby unit. Therefore, if the secondary standby unit becomes active, the
secondary unit can hand out IP addresses that the primary unit has handed out already.

Unfortunately, PIX has limited functionality in the context of DHCP. You cannot configure DHCP reservation on PIX.
Routers and servers can handle DHCP reservation. PIX can only work as:

A simple DHCP server for internal clients...

For detailed information on DHCP server, please refer Using PIX firewall DHCP server section of Using PIX firewall in SOHO networks.

 
A DHCP client for the outside interface...

DHCP client support within the PIX Firewall is designed for use within a small office, home office (SOHO) environment
using a PIX Firewall that is directly connected to a DSL or cable modem that supports the DHCP server function.

* The PIX Firewall DHCP client can only be enabled on the outside interface.

For detailed information on DHCP client, please refer Using PIX firewall DHCP client section of Using PIX firewall for SOHO networks.
 
A DHCP relay device that can pass on the DHCP information from the DHCP server to internal clients...

Acting as a DHCP relay agent, when the PIX Firewall receives a request from a host on an interface, it forwards the
request to a user-configured DHCP server on another interface.

For detailed information on DHCP relay, please refer Using DHCP relay section of Using PIX firewall on SOHO networks.

Version history
Revision #:
1 of 1
Last update:
‎06-22-2009 03:42 PM
Updated by:
 
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