Dhcp Relay Application Notes; Pat Description; Pat Application Notes - Cisco 700 Series Configuration Manual

DHCP Relay Application Notes

The following are application notes for DHCP relay:
•
The IP address in the Internal profile must be on the same network as that of the DHCP
clients.
•
A firewall configuration (where there is an Internal profile and LAN IP address) does
not work with DHCP relay.
•
A configuration where PAT is on and DHCP relay is enabled is not valid. DHCP relay
will attempt to cross from a public to a private domain. PAT prevents access to the
private domain. DHCP relay fails because it must reference the router's private address.
•
DHCP relay and DHCP server are mutually exclusive. The Cisco 700 series router can
function as one or the other, but not both.

PAT Description

Cisco 700 series routers provide PAT, enabling local hosts on a private IP network to
communicate externally.
Packets destined for an external address have their private IP address plus port number
translated to the router's external IP address before the IP packet is forwarded to the WAN.
IP packets returning to the router have their external IP addresses (plus port number)
translated back to the private IP addresses, and the packets are forwarded to the LAN.
When PAT is enabled, the transmission of RIP packets is automatically disabled to prevent
a broadcast of the private IP addresses externally.

PAT Application Notes

A configuration where PAT is on and DHCP relay is enabled is not valid. DHCP relay will
attempt to cross from a public to a private domain. PAT prevents access to the private
domain. DHCP relay fails because it must reference the router's private address.
DHCP Relay Application Notes
Configuring DHCP Relay, DHCP Server, and PAT 5-3