Troubleshooting guide

MX2820 System Manual
5-96 61186003L1-1D
Descriptions and testing diagrams of the loopback tests are provided in the following portions
of this section:
• “VT/Port Loopbacks” on page 96
• “STS-1 Loopbacks” on page 101
VT/PORT LOOPBACKS
After selecting the number that corresponds with the desired line to test, the menu illustrated
in Figure 5-64 appears. The number selected, from 1 to 28, refers to the VT number. The Port
(T1/E1) that will be tested is the port mapped to the selected VT number. The following
subsections provide descriptions and illustrations of the testing options.
Selecting option 1,
DATA MODE, will terminate a test that is in progress.
Figure 5-64. VT/Port Loopback Menu
Tributary
A Tributary loopback loops the selected VT/Port back to the network (STS-1). The T1/E1 is
looped back through the STS-1 mapper. During this loopback, the corresponding DSX-1/E1
input is overwritten by the outgoing DSX-1/E1 signal. See Figure 5-65 for an illustration of
this test.
Shelf: 1 Slot: 4A ADTRAN MX2820 System 04/15/04 13:26
Unacknowledged Alarms: NONE TID: HTVLALEXD16
VT / Port Loopbacks
VT #1 (#1 ): Data Mode
1 - Data Mode
2 - Tributary
3 - Analog Network
4 - Digital Line/Net
5 - CODEC Line/Net
6 - CSU Loopback
7 - CSU LB w/BERT
8 - Line BERT
9 - VT BERT
Selection: '?' - System Help Screen