Carnegie Mellon University Website Home Page
 

Dynamic Host Configuration Protocol (DHCP)

Overview 

The Dynamic Host Configuration Protocol (DHCP) allows networked computers or hosts to automatically obtain Internet Protocol (IP) addresses and other network attributes, such as the default gateway router, subnet mask, and Domain Name Service (DNS) servers. When a DHCP-configured host is connected to the network and either boots or attempts to reestablish connectivity, it sends a request to a DHCP server for this necessary network information. The DHCP servers centrally manage pools of this necessary network information and respond accordingly to DHCP requests. 

DHCP allows for hosts to be moved from one network to another without manual configuration, provides a mechanism for administrators to centrally manage network information, and helps prevent network outages caused by configuration issues. 

Computing Services recommends that all campus hosts use the DHCP service. 

Using DHCP on Campus 

All campus hosts must be registered in the campus network registration system (NetReg). This system automatically maintains and updates DHCP server configurations. 

There are two DHCP modes for host registrations - 'static' and 'dynamic'.  A host with a 'static' network registration will be assigned the same IP address from the campus DHCP service throughout the life of the registration, and a host with a 'dynamic' registration will be assigned a random, available IP address from the campus DHCP service.  Some campus networks permit only 'dynamic' registrations (such as the Andrew Wireless network), and Dynamic DNS (DDNS) updates are used to reflect the active IP address assigned by the DHCP service to the registered host. 

Rogue DHCP Servers

The campus DHCP service is comprised of only Computing Services' central DHCP servers. All other DHCP servers connected to campus networks that are deemed to be 'rogue' DHCP servers will be immediately disconnected from the campus network to avoid causing problems for other hosts. 

The valid campus servers are: dhcp-wired-cyh.net.cmu.local, dhcp-wired-dcns.net.cmu.local, dhcp-wifi-cyh.net.cmu.local, dhcp-wifi-dcns.net.cmu.local. If you suspect a rogue server is in operation, please contact the Help Center at 412-268-HELP(4357).