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The Leased Line Service Fails Owing to the Incorrect Modem Configurations

Publication Date:  2012-07-25 Views:  40 Downloads:  0
Issue Description

 The customer requires to implement the 3 x 64 kbit/s =192 kbit/s leased line service through the following networking:
Cisco Router-----Zentrix 3207d TDM SHDSL modem-----SDL GSHDSL port-----SDL E1 port-----DDF------CX300A-----uplink
On the UA5000, configure an intra-board semi-permanent connection from the SDL SHDSL port to the SDL E1 port (the start timeslot of the GSHDSL port is 0/15/4/0 and the end timeslot is 0/15/4/2; the start timeslot of the E1 port is 0/15/0/1 and the end timeslot is 0/15/0/3), with a bandwidth of 3 x 64 kbit/s = 192 kbit/s. After the configurations, it is found that the physical layer between the two routers is UP but the protocol layer is DOWN and that neither of the two routers can be pinged from the other. 

Alarm Information
Handling Process
1. Check the device status. The service boards work normally, GSHDSL port 0/15/4 is active, and E1 port 0/15/0 receives RRA alarm from the remote end.
2. Check the data configurations of the UA5000, focusing on the timeslot occupation and the frame format. The data configurations are all correct.
3. Connect the E1 tester to the E1 line led out of the CX. The tester works normally, which shows that the upper-layer link is normal. Connect the E1 tester to the E1 port on the SDL. The test results are all-zeros.
4. Check the Modem configurations. It is found that DIVCLOCK is set to 1. Change the DIVCLOCK setting to normal, save the data, and restart the Modem. After that, the state of the protocol layer is changed from DOWN to UP, and the two routers can be pinged from each other. The fault is removed.
Root Cause

The possible causes are as follows:

1. The physical connection is faulty.
2. The upper-layer link is faulty.
3. The data configurations are incorrect.
4. The Modem configurations are incorrect.

When one timeslot is required to provide a 64 kbit/s service, you need to set DIVCLOC to 1. When three or more timeslots are required, you need to set DIVCLOCK to NORMAL.