1
DHCP RELAY
1.1DHCP Relay
This application describes the functionality of the DHCP relay feature and includes CLI command examples.
1.1.1 Feature Overview
Black Box DHCP relay feature eliminates the need for a DHCP server on every LAN, because DHCP requests can be relayed to a single remote DHCP server. Black Box’s implementation of DHCP relay is based on RFC 1532. BOOTP/DHCP messages are relayed (vs. forwarded) between the server and client.
Figure 1 DHCP Relay Overview
LAN |
|
| DHCP Relay Agent |
LAN | WAN |
DHCP Relay Agent | LR1104A | DHCP Server |
LAN
LR1114A |
|
|
DHCP Relay Agent | ||
1.1.2 Functionality
The DHCP relay feature uses BOOTP requests and replies to negotiate packet delivery between the DHCP client and server.
1.1.2.1 BOOTP Requests
BOOTP requests are messages from client to server. Request messages include DHCP DISCOVER, DHCP REQUEST, DHCP RELEASE, etc. The relay agent modifies the packet header by adding relay information to the DHCP gateway address (giaddr) field. The server replies to the gateway address specified in the packet’s giaddr field.
