Troubleshooting guide

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Cisco Broadband Local Integrated Services Solution Troubleshooting Guide
OL-5169-01
Chapter 9 Troubleshooting Cisco Media Gateways
Data Path Troubleshooting
Line Interface and Switching Path Troubleshooting
Line interface and switching patch troubleshooting is necessary when problems occur with any of the
following:
• DS1 line interface
• E1 line interface
• DS3 line interface
• OC3 line interface
• ATM switching path components
Most line interface symptoms are caused by improper hardware configuration, such as cabling.
Other problems may be caused by the following:
• Software configuration, such as clocking, line type, encoding, and framing mismatch
• System configuration, such as DMC M13 mapping
• Genuine hardware failures which do occur (although rarely), such as broken optical cable,
connectors
E1 Line Interface Debug Methodology
• Always capture the output of lsevt, lstraps, and E1 CLI and engineering debug commands
• Always issue lsds1ln to verify configuration and check alarm status and alarm cause. Verify that the
E1 line has not been mistakenly put in loopback state.
• Always issue lsds1curst and lsds1totst to inspect performance statistics; perform lsds1curst multiple
times to detect trends
• RED - LOS - check cables; in case of BSC/DMC 1:1 redundancy also check the corresponding DS3
Y-cables
• RED - LOF – confirm near end and far end have the same line type (DS1 vs. E1) and framing type
(ESF, D4, E1-CRC-MF etc.)
• YELLOW – the remote end is in RED alarm
If performance statistics show recurring control slip seconds (in output of lsds1curst or lsds1totst), verify
that the various nodes in the network are configured to have the SAME reference clock source. For
multi-chassis and PRI type of applications, the various nodes in the system must have the same reference
clock to synchronize clock sources.
If BOTH local and remote end DS1 lines are in RED, isolate fault by first putting remote end in LINE
loopback (either by performing line loopback on remote node directly or by sending loopback code from
local end using chds1ln). Then initiate BERT test (using onbertds1) from local end to verify local side.
Remember to UNDO loopback on remote end.
Special case 1: No voice when the MGX8260 is connected to E1 channel bank
Make sure the E1 line robbed bit signaling is turned on and the correct robbed bit pattern (0101) is
selected.
Special case 2: DMC M13 mapped NSC DS1 lines in RED alarm
Use lsm13s to verify M13 mappings; use lsds3ln to verify the mapped DMC DS3 line state