DHCP (Dynamic Host Configuration Protocol) lets you dynamically get an address from a server
- Uses UDP
- Only hold address while connected/on
- Allows reuse of address
- Can renew lease on address in use
- Support for mobile users who want to join network
In addition to IP Address, also returns:
- Address of first-hop router for client
- Name and IP address of DNS server
- Network mask (to indicate network vs host portion of address)
Steps:
- Client sends DHCP discover packet
- DHCP server sends DHCP offer
- Client sends DHCP request
- DHCP server sends DHCP ACK
All of these steps are done on broadcast address so that all computers on network know about the new kid
- DHCP server maintains pool of available addresses
- There is at least one DHCP server for an administrative domain (a server or relay agent per subnet)
DHCP Lease
DHCP lease time: the amount of time the IP address is granted to a device
- Must be renewed before lease time expires
- Or ask for new IP address after lease time expires