DHCP
A DHCP server allows the client to get an IP address automatically without having to manually configure a static IP.
Ports
DHCP servers also use port 67 to initiate communication between the client and server on the network. If port 67 is used by another application, DHCP will fail to function. Clients use port 68.
DHCP relay
DHCP relay listens to local broadcast messages from client and forwards these messages on another network towards the DHCP server. The DHCP server responds and the replies is then forwarded back to the client.
DHCP proxy
DHCP proxy is a fully-functional DHCP server and client built inside. The client establishes IP leases from the DHCP server on one interface, and then keeps these addresses in a pool. On another interface, the server side of the implementation provides leases to other machines using that pool.
Example
Cisco PIX/ASA Firewalls supports both method. Generally, the FW interface on which it behaves as a DHCP server has a dedicated, manually-configured address pool, and the only thing the proxy feature does is get configuration parameters from another upstream server.[1]
Reference
[[Category: Terminology]]