Using Loopback Commands - Cisco ASR 1000 Series Software Configuration Manual

Troubleshooting the Serial SPAs
Field
Interval: 5 minute(s), Time Remain: 5 minute(s)
Bit Errors (Since BERT Started): 6 bits
Bits Received (Since BERT start): 8113 Kbits
Bit Errors (Since last sync): 6 bits
Bits Received (Since last sync): 8113 Kbits

Using loopback Commands

Loopback support is useful for testing the interface without connectivity to the network, or for diagnosing
equipment malfunctions between the interface and a device. The 2-Port and 4-Port T3/E3 Serial SPA supports
both an internal and an external loopback mode. The external loopback mode requires the use of a loopback
cable and implements a loopback through the transceiver on the SPA.
You can also configure an internal loopback without the use of a loopback cable that implements a loopback
at the PHY device internally. By default, loopback is disabled.
To configure loopback, use the following commands:
Command
Router# configure terminal
T3/E3
Router(config)# interface serial slot/subslot/port
T1/E1
Router(config)# controller slot/subslot/port
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Cisco ASR 1000 Series Aggregation Services Routers SIP and SPA Software Configuration Guide, Cisco IOS XE
Using loopback Commands
Description
Indicates the time the test takes to run and the time
remaining for the test to run.
If you terminate a BER test, you receive a message
similar to the following:
Interval: 5 minute(s), Time Remain: 2
minute(s) (unable to complete)
"Interval: 5 minutes" indicates the configured run time
for the test. "Time Remain: 2 minutes" indicates the
time remaining in the test prior to termination.
"(unable to complete)" signifies that you interrupted
the test.
These four lines show the bit errors that have been
detected versus the total number of test bits that have
been received since the test started and since the last
synchronization was detected.
Purpose
Enters global configuration mode.
Selects the interface to configure and enters interface
configuration mode.
• slot/subslot/port—Specifies the location of the
T3/E3 interface.
• slot/subslot/port—Specifies the location of the
T1/E1 controller.
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