Cisco® Field Manual: Catalyst® Switch Configuration

Back-to-Back Connections

In a lab setup or in certain circumstances, you might find that you need to connect two switches or two routers to each other in a back-to-back fashion. Normally, some other active device is used to connect router interfaces. For example, an Ethernet hub or switch, a Token Ring media attachment unit (MAU), and the Public Switched Telephone Network (PSTN) all perform an active role in interconnecting routers. If these are not available, as in a lab environment, a special cable is needed to make the back-to-back connection.

NOTE

It is not possible to make a back-to-back cable to connect two Token Ring interfaces. Token Ring connections require an active device such as a MAU or a Token Ring switch to terminate the connection. ...