CANOGA PERKINS CanogaOS Configuration Guide - Manual (Page 296)

CanogaOS Configuration Guide
Proprietary & Confidential Canoga Perkins Metro Ethernet Switches Page 296 of 350
35 Configuring DHCP
35.1 DHCP Relay Configuration
DHCP relay agent is any host that forwards DHCP packets between clients and servers. Relay
agents are used to forward requests and replies between clients and servers when they are not on
the same physical subnet. Relay agent forwarding is distinct from the normal forwarding of an IP
router, where IP datagrams are switched between networks somewhat transparently. By contrast,
relay agents receive DHCP messages and then generate a new DHCP message to send out on
another interface. The relay agent sets the gateway address (giaddr field of the DHCP packet)
and, if configured, adds the relay agent information option (option82) in the packet and forwards
it to the DHCP server. The reply from the server is forwarded back to the client after removing
option 82.
35.1.1 References
The DHCP Relay module is based on the following RFC:
RFC 1542 and RFC 3046
35.1.2 Terminology
Following is a brief description of terms and concepts used to describe the DHCP Relay:
Dynamic Host Configuration Protocol (DHCP)
Dynamic Host Configuration Protocol (DHCP) is a client/server protocol that automatically
provides an Internet Protocol (IP) host with its IP address and other related configuration
information such as the subnet mask and default gateway.
CHADDR
Client Hardware Address field in the DHCP payload.
GIADDR
Gateway IP Address field in the DHCP payload.