Relay Agent
If DHCP or BOOTP servers are present in remote locations, clients cannot reach them because the limited broadcast IP address, which is used to send the request, is valid only within local area networks. In such cases, routers that are configured as relay agents can be used to transfer the messages between the server and the client. Relay agents, also called helpers, act as forwarding agents that are used by UDP on port 53 to forward messages to clients located in remote locations.
When a relay agent receives a request message, it adds its IP address in the Gateway IP Address field and passes the message to the server. On receiving the reply from the server, the agent forwards the message to the client.
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