DHCP server

In short: A DHCP server is the service that automatically assigns IP addresses and other settings to devices in a network.

In more detail: In home networks it is built into the router, in companies it usually runs on a Windows or Linux server. It works with the DHCP protocol (the DORA sequence) over UDP, server port 67 and client port 68.

In Depth

• Address pool (scope): the range from which addresses are handed out, e.g. 192.168.1.100 to 192.168.1.200.
• Lease: each address is only lent for a certain time.
• Reservation: a device always gets the same address based on its MAC address.
• Options: besides the address it delivers the subnet mask, default gateway and DNS server.
• Only one per network: two DHCP servers in the same network can hand out conflicting addresses. Exceptions are coordinated failover pairs.
• Relay: a router can forward requests across network boundaries to a central DHCP server.
• Checking: ipconfig /all shows the DHCP server and the lease, ipconfig /renew requests a new address.

See also: DHCP, ipconfig