Specifications

CHAPTER
8-1
Cisco MGX 8260 Command Line Interface Guide
Release 1.2, Part Number 78-10987-01 Rev. B0, January, 2002
8
Troubleshooting
The MGX 8260 Media Gateway includes diagnostic features that facilitate fault location, such as
loopback and bit error rate tests. See the following sections for information on how to locate and clear
trouble conditions.
• Performing Loopback Tests
• Performing BERT Tests
• Clearing Alarms
Performing Loopback Tests
Loopback tests are powerful troubleshooting tools that help maintenance personnel locate faults along
the transmission path. DS1/E1 and DS3 lines provide both local and line loopbacks.
Figure 8-1 DS1/E1 and DS3 Loopback Options
The local loopback option loops the DS1 signal back towards the backplane and helps isolate problems
on the MGX 8260 side of the signal path. The line loopback option loops the signal back towards the
DS1 or DS3 line and helps identify problems in the signal path between the MGX 8260 Media Gateway
and other network equipment. A third option, payload loopback, is similar to line loopback, except that
the RX signal loops through the card’s DS1 or DS3 framer logic before being returned on the TX line.
Payload loopback helps determine whether the card itself is functioning properly.
31936
DS1 or DS3
front card
DS1 or DS3
back card
Fr.
Line
RX
TX
Payload
Loca
l