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Network Protocol Addresses

A communications protocol is the set of standards used by two processes that communicate with each other. It can be thought of as a set of rules or the language for communication. One host may use several protocols to communicate over the network. Each of these protocols provide a way to identify a particular host on the network; specifically, a network address, and each protocol uses its own form of address. An address is just a designation that uniquely identifies an endpoint of a connection, like a telephone number. Just like telephone numbers, addresses used by communications protocols must be assigned so that one endpoint can be found from anywhere on the network. Network addresses may be divided into heirarchical subnetworks (also called subnets), much like the telephone system is divided by area codes and exchanges. The protocols most commonly used on Virginia Tech's network and the principal topic of this section are the Internet Protocols, IPv4 and IPv6 (collectively, "IP").

In order for a host to communicate, it must use an address that is assigned to it based on its location in the network. This assignment may be automatic (as with IPv6 with SLAAC, or IPv4 with DHCP) or it may require configuration by the system manager (as is often the case with static IP addresses). Since numeric addresses are inconvenient for people to use and remember, addresses should be associated with names. Naming hosts is discussed later in this document.

Most of the notes and conventions about assigning IP addresses here are only valid for users on wired networks. There is more documentation on wireless elsewhere in this document.

Internet Protocol (IP)

IP is the Internet Protocol. It is used throughout the worldwide Internet (estimated to interconnect more than 3.2 billion people and hosts), and is the only protocol that is supported on all parts of Virginia Tech's network. It is well-documented and designed to work under the worst network conditions.

There are 3 major types of IP addresses in use on Virginia Tech's Campus: global IPv4 addresses like, private IPv4 addresses (also refered to as RFC1918 addresses) like, and global IPv6 addresses like 2607:b400::43af:0:4521


Each host running IP must have an IP address. An IPv4 address is usually expressed as four numbers (each less than 255) separated by periods, e.g. As discussed above, an IP address is determined by the location of the network connection. A particular IP address is only valid within one subnet. In most cases, one subnet will serve only one or just a few buildings. When requesting addresses, be sure to specify the building where they will be used so that the hostmaster can assign an address in the proper subnet.

The NL requests static IPv4 addresses by sending mail to indicating the number of addresses needed, building, and sub-domain (the sub-domain is part of the host name, and is discussed later). It is usually a good idea for the NL to have a few spare addresses for testing and future assignment. It is important that the NL understand where the assigned addresses will work. The NL then passes this information on to the individual users requesting addresses. The NL should be sure to give the user other configuration information such as gateway, netmask, broadcast address, domain name servers, time servers, etc.

It is also possible to register hosts for Dynamic Host Configuration (DHCP). Any user with an active network portal and a PID may do this themselves.


IPv6 is the next generation of the internet protocol, and shares many similarities with IPv4. The most profound differences for most users is that IPv6 has a 128-bit address space, and thus addresses are much longer.

NI&S does not currently manage allocation of IPv6 addresses; most hosts will by default automatically configure one or more IPv6 addresses using StateLess Address AutoConfiguration (SLAAC). However, should users wish to assign static IPv6 addresses, we have tools to assist NLs in allocating them and avoiding collision with other users. The hostmaster will assign you an Organizationally Unique Identifier (OUI) which can be used in your IPv6 addresses. When you request an OUI, you will also be sent a list of randomly generated host suffixes with that OUI, that you can use on any subnet on-campus. An example of this data file is here, showing sample usage for assigning OUIs to host names.

Next: IP Domain Names Up: Network Liaison's Handbook Previous: Network Liaison's Functions

Phil Benchoff, Eric C. Landgraf 2019-05-07