What is DHCP and how does a DHCP relay agent enable IP configuration across subnets?

• A. DHCP is for DNS configuration; relay agent translates hostnames.
• B. DHCP dynamically assigns IP, mask, gateway; relay agent forwards client broadcasts to central DHCP server across subnets, adding giaddr.
• C. DHCP only assigns IPs on the local subnet; relay agent blocks DHCP requests.
• D. DHCP assigns static IPs only; relay agent caches IP addresses.

Answer: (B)

DHCP dynamically assigns IP configuration such as an IP address, subnet mask, and default gateway to clients, so devices can join networks without manual setup. When clients are on different subnets, a router typically blocks DHCP broadcasts from reaching a server on another subnet. A DHCP relay agent solves this by receiving the client’s DHCP broadcast and forwarding it to a central DHCP server across subnets, while adding the giaddr (gateway IP address) field to indicate the client’s subnet. The central server uses that giaddr to select the correct IP pool and to route the server’s reply back through the relay to the client. In short, DHCP provides automatic IP configuration, and a relay agent enables that across subnets by forwarding requests and tagging them with the client’s subnet information.