Full form: Dynamic Host Configuration Protocol
Also known as: Dynamic Host Configuration Protocol
Quick Definition
A protocol that automatically assigns IP addresses and network parameters to clients.
DHCP automates IP address assignment. Clients send a DISCOVER broadcast, servers respond with OFFER, clients send REQUEST, and servers confirm with ACK — remembered as DORA. DHCP assigns IP address, subnet mask, default gateway, DNS server, and lease duration. Cisco routers can act as DHCP servers, relay agents (ip helper-address), or clients. The relay agent (ip helper-address) forwards DHCP broadcasts to a server on a different subnet.
ip dhcp pool SALES network 192.168.1.0 255.255.255.0 default-router 192.168.1.1 dns-server 8.8.8.8 ip dhcp excluded-address 192.168.1.1 192.168.1.10
DHCP uses UDP ports 67 (server) and 68 (client). DHCP DISCOVER is a broadcast — it does not cross router boundaries without an ip helper-address configured on the router interface facing the clients.
DHCP automates IP address assignment. Clients send a DISCOVER broadcast, servers respond with OFFER, clients send REQUEST, and servers confirm with ACK — remembered as DORA. DHCP assigns IP address, subnet mask, default gateway, DNS server, and lease duration. Cisco routers can act as DHCP servers, relay agents (ip helper-address), or clients. The relay agent (ip helper-address) forwards DHCP broadcasts to a server on a different subnet.
DHCP uses UDP ports 67 (server) and 68 (client). DHCP DISCOVER is a broadcast — it does not cross router boundaries without an ip helper-address configured on the router interface facing the clients.
DHCP falls under the IP Services domain of the 200-301 exam. Understanding it in context with related terms like dns and dhcp-snooping is essential for answering scenario-based questions correctly.