Using 56k cards instead of serial cards

In some of our lab rooms you will find 56k cards instead of serial cards. Because we frequently plug and unplug these connections the 56k cards (with RJ-45 connectors) are more reliable and don't wear out as fast as the serial cards do. There are a few changes you need to be aware of though when using these cards.

Different Port Naming

Because the regular serial cards have two ports on one card they are identified as Serial0/0/0 and Serial0/0/1. Because each 56k card has only one port on it they are identified as Serial0/0/0 and Serial0/1/0. See the table below for a mapping:

Traditional Serial Port	56k Card Port
Serial0/0/0	Serial0/0/0
Serial0/0/1	Serial0/1/0

Port Clocking

All serial connections require a clock signal of some kind so the other end knows when to read a bit from the line, the serial connections on a router are no exception. Both traditional serial ports on the routers and the 56k cards use clocking but they are configured differently. On a traditional serial port you simply set the clock rate on the DCE end of the connection with the clock rate <bits per second> or clockrate <bits per second> command but this will not work on the 56k cards. There are no DTE and DCE ends Instead you must set one of the two routers as the clock source and the other as the clock recipient. This is done with the service-module 56k clock source internal and service-module 56k clock source line commands as well as the service-module 56k network-type dds command on both ends. Finally the cards must have the speed set with the service-module 56k clock rate <kbps> command.

Cable End	Traditional Serial Port	56k Card Port
DTE	No special programming.	service-module 56k clock source line service-module 56k network-type dds service-module 56k clock rate 56
DCE	clock rate 128000	service-module 56k clock source internal service-module 56k network-type dds service-module 56k clock rate 56