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Network Warrior, 2nd Edition by Gary A. Donahue

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Configuring T1s

There are two steps involved in configuring T1s for use on a router. The first step is the configuration of the CSU/DSUs. The second step is the configuration of the router interface. When you’re using integrated CSU/DSUs, the lines might seem blurred, but the concepts remain the same. Configuring the router interface is just like configuring any serial interface.

CSU/DSU Configuration

To get a T1 up and operational, you must do the following:

Configure both sides with the same encoding that matches the circuit’s provisioned encoding

Encoding options are AMI and B8ZS. Data T1s should always use B8ZS encoding. To configure encoding on a CSU/DSU WIC, use the service-module t1 linecode interface command:

Router(config)#int s0/1
Router(config-if)# service-module t1 linecode b8zs
Configure both sides with the same framing that matches the circuit’s provisioned framing

Framing options are D4/SF and ESF. Data T1s should always use ESF framing. To configure framing on a CSU/DSU WIC, use the service-module t1 framing interface command:

Router(config)#int s0/1
Router(config-if)# service-module t1 framing esf
Configure how many channels will be used for the link, which channels will be used, and what speed they will be

If the T1 is being split or you have had fewer than 24 channels delivered to you, you must tell the CSU/DSU how many channels are in use. You do this for the CSU/DSU WIC with the service-module t1 timeslots interface command. Here, I’ve specified that channels 7–12 will ...

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