Configuring a Serial Interface

Although this is a slightly more complex process that configuring an Ethernet interface, it only contains a few more steps.

You must:

1. Set the interface IP address and subnet mask.
2. Set clock rate if a DCE cable is connected. Skip this step if a DTE cable is connected.
3. Turn on the interface.

DCE/DTE – Interface types
DTE is short for Data Terminal Equipment, a device that controls data flowing to or from a router.

The term is most often used in reference to serial communications defined by the RS-232C standard. This standard defines the two ends of the communications channel as being a DTE and Data Communications Equipment (DCE) device.

In practical terms, the DCE is usually a modem or some network device that controls the clocking rate (this is usually controlled by the telecommunications company) and the DTE is the router

Therefore these connections that exist on either end of a WAN connection. As we can only simulate a WAN we need to make one router simulate the DCE connection and the other a DTE connection. As the DCE connection controls the line speed, we must put a clockrate on the interface. There are various speeds we can use, an example would be 64000.

The basic configuration of a serial connection is no different than the other types of connections.  You would enter Interface Configuration mode, set the IP address, and remove the shutdown command. Below is a sample set of code to set up a DTE end serial connection

Router1#config terminal
Router1(config)#interface serial 0/0
Router1(config-if)#ip address
Router1(config-if)#no shutdown

In order to set up the DCE end you would setup the interface in a similar method to the one above, REMEMBER that you need to add the clockrate command; see below

Router2#config terminal
Router2(config)#interface serial 0/1
Router2(config-if)#ip address
Router2(config-if)#clock rate 64000
Router2(config-if)#no shutdown

Remember to issue you copy running-config startup-config (or copy run start for short to save your configuration to NVRAM)

Next – Interface Descriptions