DHCP and BOOTP Relay Overview
You can configure a Juniper Networks switch to act as a Dynamic Host Configuration Protocol (DHCP) or Bootstrap Protocol (BOOTP) relay agent. This means that if the switch receives a broadcast DHCP or BOOTP request from a locally attached host (client), it relays the message to a specified DHCP or BOOTP server. You should configure the switch to be a DHCP/BOOTP relay agent if you have locally attached hosts and a distant DHCP or BOOTP server.
If you configure a switch to be a DHCP relay agent, you can also enable smart DHCP relay, which enables you to configure alternative gateway addresses for a DHCP server so that if the server fails to reply to the requests sent to the primary gateway address, the switch can resend the requests to the alternative gateway addresses. To use this feature, you must configure a routed VLAN interface or Layer 3 subinterface with multiple IP addresses and configure that interface to be a relay agent.
 | Note: Because DHCP and BOOTP messages are broadcast and are not directed to a specific server, switch, or router, Juniper switches cannot function as both a DHCP server and a DHCP/BOOTP relay agent at the same time. The Junos operating system (Junos OS) generates a commit error if both options are configured at the same time, and the commit operation does not succeed until one of the options is removed. |
