3Com 3C8S5007 - SuperStack II PathBuilder S500 Switch User Manual page 124

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PPENDIX ROUBLESHOOTING
For Flex-WAN serial interfaces, place the modem or CSU/DSU in local
loopback test mode. For information, see the documentation that
accompanies your modem or CSU/DSU.
For Ultra-WAN CSU/DSU interfaces, ensure that the central office/PTT
switch is configured for loopback in the manner shown for the "link
partner" in Figure 44. If you are interfacing to an external CSU, place
the CSU in the local loopback test mode.
Verify the path and port number of the WAN interface you are testing
by referring to Figure 12, Figure 13, or Figure 14 in the "Basic
Configuration of Ports, Paths, and Connectors" chapter.
To perform the loopback test, follow these steps:
1 For Flex-WAN interfaces, set the line type to Leased using:
SETDefault !<path> -PATH LineType = Leased
For UltraWAN interfaces, set the connector type to either E1 Unstructured
or T1 Unstructured using:
SETDefault !<path> -PATH CONNector = E1_U
or
SETDefault !<path> -PATH CONNector = T1_U
2 Set the port owner of the Flex-WAN serial interface you are testing to
LoopBack using:
SETDefault !<port> -PORT OWNer = LoopBack
3 Select the loopback test mode by entering:
DLTest TestMode LoopBack
4 Specify the number of seconds that the test should run using:
DLTest TestDuration <seconds>
If you do not enter a value, the test will run indefinitely. However, use
caution when running the test for a specified duration. The test ends
abruptly as soon as the time duration expires, and a discrepancy between
the number of packets transmitted and the number received may result.
5 Start the loopback test by entering:
DLTest START
If the number of received packets equals or approximately equals the
number of transmitted packets, your serial line has passed the loopback