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Document ID: 10288
Contents
Back-to-Back Setup
Before You Begin
Conventions
Prerequisites
Constructing a Cross-Over Cable
T1 CSU/DSU Cross-Over Pinout
56k CSU/DSU Cross-Over Pinout
T1 CSU/DSU Configuration
Four-Wire 56k CSU/DSU Configuration
Related Information
Back-to-Back Setup
The Cisco 2524-2525 can be used in back-to-back configurations with the T1 CSU/DSU and the four-wire 56k CSU/DSU using a cross-over cable between the CSU/DSUs. The two-Wire CSU/DSU cannot be configured for back-to-back operation in this manner. Back-to-back configuration of the 4-wire CSU/DSU has the following restrictions:
-
You cannot use a clock rate of auto on either side of the back-to-back setup
-
You cannot use a clock rate of 64 .
-
You cannot use switched-56 operation .
Before You Begin
Conventions
For more information on document conventions, see the Cisco Technical Tips Conventions.
Prerequisites
There are no specific prerequisites for this document.
Constructing a Cross-Over Cable
The T1 CSU/DSU has a different pinout than the four-wire 56k CSU/DSU. The connector for the T1 CSU/DSU is an RJ-48C. The connector for the four-wire 56k CSU/DSU is an RJ-48S. Both connectors are compatible with RJ-45 plugs.
T1 CSU/DSU Cross-Over Pinout
|
From RJ 48C Pin |
To RJ-48C Pin |
|---|---|
|
1 |
4 |
|
2 |
5 |
|
4 |
1 |
|
5 |
2 |
56k CSU/DSU Cross-Over Pinout
|
From RJ 48S Pin |
To RJ-48S Pin |
|---|---|
|
1 |
7 |
|
2 |
8 |
|
7 |
1 |
|
8 |
2 |
Tip: You can actually use a Cisco rolled RJ-45 cable (CAB-500RJ=) as a four-wire 56k cross-over cable. Even though the polarity is wrong, the bi-polar signal will be interpreted correctly by the CSU/DSU.
Tip: Make sure you count the RJ-45 pins as shown in the illustration below:
T1 CSU/DSU Configuration
Set one CSU/DSU to clock source internal, and the other CSU/DSU to clock source line. The linecode, framing, data-coding, and timeslots must be set the same on both CSU/DSUs.
Four-Wire 56k CSU/DSU Configuration
Set one CSU/DSU to clock source internal, and the other CSU/DSU to clock source line. On the CSU/DSU with internal clock, the clock rate must not be auto. Both CSU/DSUs must be set for service-module 56k network-type dds.
Related Information
| Updated: Sep 09, 2005 | Document ID: 10288 |