RFC 2131 / START HERE
DHCPv4, before the details
DHCP: Dynamic Host Configuration Protocol
DHCP gives devices IPv4 network settings automatically, often including an address and how to reach the local router.
The idea in one picture
A device joins the network
DHCP offers a lease
The device gets network settings
A simplified picture of the idea; the chapters explain the actual mechanisms.
Why it exists
Manually configuring every device is tedious and error-prone. DHCP allows a network to lend addresses for a limited time and manage their reuse.
A familiar example
A laptop joins home Wi-Fi and obtains an IPv4 address from the router's DHCP service.
Helpful background
You can start here without reading another RFC. If these ideas are unfamiliar, these short introductions may help.
What you’ll learn next
Begin with chapter one, or choose a topic.
- Discover and select an addressA new client discovers servers, selects an offer, and requests the chosen allocation before using it.→
- Reach a server through a relayA relay carries DHCP between a client’s local network and a server elsewhere. Its giaddr field supplies relay context.→
- Renew before the lease expiresA bound client first renews with its original server, then tries any server, and finally stops using an expired address.→
- Validate a remembered addressA restarted client can ask to reuse an earlier address. Remembering it does not establish that it remains valid on the current link.→
- Check conflicts and release addressesA client checks an offered address before use. Discovery of a conflict and voluntary release are different protocol messages.→
- Request settings without a leaseA device with an externally configured IPv4 address can request other configuration using DHCPINFORM.→
This introduction explains RFC 2131 (1997). Read the original RFC ↗