Introducing the Campus DHCP Service
In order to use the campus network, all devices connected to it
must be configured with a number of different parameters. The Dynamic
Host Configuration Protocol (DHCP) automatically configures network
devices with the parameters they need to utilize the network. DHCP is
an alternative to manual configuration of these parameters. The
campus DHCP service is available on the campus wired network. In order to make use
of the service, a network device must be registered with
the service and it must be configured to use DHCP to obtain its
network settings. A web application is available for self service
registration of devices by students, faculty and staff.
Originally called the Laptop IP Service (LIPS), the
service has expanded to support configurations required by less
transient devices (such as desktops and printers) and is available for
use with any device supporting DHCP connected to the campus wired
network supported by Information Services and Technology (IST).
The campus DHCP service is provided by IST. The campus Hostmaster
supports DHCP registration and configuration
activities. Infrastructure Services develops, troubleshoots and
operates the service.
Registering a Device with the Campus DHCP Service
To register a device, you first need to determine the hardware address
of the device's wired network interface. The hardware address is
commonly called the Ethernet address or the Media Access Control (MAC)
address. See the FAQ for more information on locating your device's
hardware address. Make sure you find the hardware address for the
wired network connection to the campus network; your device may have
multiple network connections (including wireless) that each have
different hardware addresses.
With the hardware address is hand, log in to the
registration web application.
Type in the hardware address and click register. Your registration
will take effect immediately. Registration via the web application
allows the registered device to obtain dynamic DHCP service on any
network with available addresses.
Methods of Address Assignment and DHCP
When a DHCP server assigns an IP address to a device, the assignment -
called a DHCP lease - is of finite duration. DHCP allows devices to
renew leases to continue to use an IP address beyond the time the
device's current lease is valid. After a DHCP lease for an IP address
expires without renewal, the DHCP server may issue a lease for the IP
address to a different device. There are two important implications of
this behavior. First, the use of finite duration DHCP leases permits
the DHCP server to automatically reuse IP addresses, encouraging more
efficient use of IP address space. Second, a device may get a
different IP address each time it requests a lease.
The change of the IP address assigned to a device over a period of
time can present some problems in certain cases. The device may
run a protocol, such as NFS, that doesn't handle changes in IP addresses well.
The device may run a service, such as remote desktop, where the user
of the device wishes to have a constant identifier for connecting to
the service. The campus DHCP service has features - fixed assignment
of IP addresses and dynamic DNS, discussed below - to address these
IP addresses are assigned to network devices for use on the campus
network in one of three different ways.
- Static assignment of an IP address to a network connection
(identified by the connection's cable identifier) is performed by the
campus Hostmaster; this form of assignment does not involve
DHCP. Using the information provided by Hostmaster, the administrator
of the device must manually configure various parameters (IP address, subnet mask, gateway, nameserver IP addresses) for operation
on the network.
- Fixed assignment of an IP address (commonly called fixed DHCP) to a device is performed by
the campus Hostmaster. The hardware address of the device should be
registered with the campus DHCP service prior to contacting Hostmaster
to request a fixed assignment. By default, the generic hostname for
the IP address associated with the fixed assignment is placed in the
departmental or other specific subdomain associated with the
subnet. Custom hostnames, aliases and other DNS records associated
with the IP address of a fixed assignment may be requested along with
the fixed assignment request.
- Dynamic assignment of an IP
address (commonly called dynamic DHCP) to a device is performed
by the DHCP servers as part of assigning a DHCP lease to the device. A
single device may receive a different IP address each time it connects
to the network. IP addresses are automatically recycled after
use. Before dynamic assignment is used on a subnet, the contact for
subnet must ask the campus Hostmaster to create a pool of addresses
for dynamic assignment. The hostnames for IP addresses in dynamic
pools are placed in the LIPS.Berkeley.EDU subdomain; see the FAQ for details.
For information on the mechanics of arranging service, please see the FAQ.
The different types of service exist to meet the different needs of
devices attached to the campus wired network.
For most devices,
dynamic assignment is the recommend choice. Dynamic assignment does
not require campus Hostmaster interaction; it is the default type of service for all registrations made via the self service registration web page. IP addresses are automatically
recycled as devices connect to the network and leave it. Dynamic DNS
provides a way for users of services on the device (such as remote
desktop) to connect to the device using a single hostname regardless
of the IP address the device is using.
Fixed assignment is useful in situations where a device makes use of
a protocol that does not handle changes in the device's IP address
gracefully (e.g. NFS). Devices that provide a commonly used service
(e.g. printers) are also candidates for fixed assignment.
Static assignment is required when a device does not support
DHCP. Servers or other critical infrastructure are also candidates for
Dynamic DNS with DHCP
Dynamic DNS allows the campus DHCP servers to associate a hostname in the
DNS with an IP address at the time the IP address is assigned to a
device as part of a DHCP lease. When the DHCP lease expires, the
hostname is removed from the DNS. By associating a hostname with a
device, dynamic DNS ensures that whenever the device has an IP address
assigned by the campus DHCP servers the device is reachable via its
hostname. Dynamic DNS requests are handled by the campus Hostmaster. For
information on the mechanics of requesting dynamic DNS service, please
see the FAQ.
Dynamic DNS is only available when dynamic address assignment is
used. With fixed assignment, DNS records are associated with the IP
address of the fixed assignment.
All dynamic DNS hostnames are in the subdomain dyn.Berkeley.EDU.
Monitoring and Measurement
Improving monitoring and measurement related to the DHCP service is an
active project. Measuring utilization of dynamic pool addresses is
useful given the "first come, first served" nature of these
pools. When a dynamic pool runs out of addresses, no additional
devices may obtain an address from the pool. It is helpful, both
for troubleshooting and capacity planning, to know what the
utilization of dynamic pool address space has been and is
currently. DHCP dynamic pool address utilization graphs
provide current and historical information on pool usage for each
subnet with a dynamic pool. These graphs show the dynamic addresses in
use, measured in five minute intervals, as well as the number of
addresses in dynamic the pool. Please note that the system used to
produce these graphs is not yet complete and the graphs are offered
here as a pilot test of the system.
Support for the Campus DHCP Service
DHCP registration and configuration support is provided by the campus
No central support is available for device configuration; the Departmental On-site Computing
Support (DOCS) service is available on a contract basis for device
support for faculty and staff. Students may contact the Student Computer Consulting
Service for support.
Correctly configured and registered devices that experience problems
with the DHCP service should be reported to the IST Service
Desk as a network problem.
Mailing lists related to the Campus DHCP Service
Outage and maintenance announcements for DHCP are sent to the UCB Net Announce
email list described on the Emergency Maintenance and Planned Outages web page. Also check the
IST Service Status page for
current maintenance. Two other DHCP specific mailing lists are intended for non outage or maintenance
announcements as well as discussion of the service. These mailing
lists are hosted on CalMail
and are firstname.lastname@example.org
All service requests and questions should be directed to the campus
please see the FAQ for details.