Some computer network hardware features uplink ports designed for plugging in network cables. These ports allow a network to communicate with other outside networks. Uplink ports on home routers, for example, allow connecting to broadband modems and the Internet.

Ethernet hubs, switches,​ and routers traditionally designate one of their Ethernet ports as the uplink connection that is specially marked on the unit by name and/or color. Home broadband routers usually label this port “WAN” or “Internet” instead of “uplink,” but the concept and function are the same.

Uplink connections uses include:

Conversely, uplink connections should generally do not include:

Note that, in modern computer networks, connections are bi-directional. Even for connections to an uplink port, the same cable or wireless link can transfer data both from and to devices on either end rather than only “up” or “down.” The terms uplink and downlink here apply to which end of the connection initiates a data transfer.

Networking professionals may point out that an Ethernet crossover cable can be used for connecting a computer to an uplink port or connecting two uplink ports to each other. While technically correct, the usefulness of these types of connections is limited.

The traditional hardware logic of an uplink port supports only network uplink devices. However, many modern home broadband routers offer a dual-purpose port instead, one that can function either as an uplink or a standard port depending on the type of device connected to it.

Before dual-purpose ports became popular, some older network equipment specially configured a standard port next to the uplink one and linked the two together as a pair. Specifically, the hardware logic of these products supported connections to either the uplink port, or the standard shared port, but not both. Connecting devices to both ports of a shared port device stop the unit from functioning properly.