Troubleshooting guide

5-15
ATM and Layer 3 Switch Router Troubleshooting Guide
OL-1969-02
Chapter 5 Troubleshooting Switch Router ATM Interface Connections
Common show controller Troubleshooting Fields
Port Status and Active Defects
In a normal state the Port status field indicates “Good Signal” and Active Alarms and the Active Defects
fields should be empty. These show controller command fields indicate the following:
• Port status field displays one of the following:
– Good Signal—indicating a good connection
– Invalid—indicating the port is administratively down
– Displays an alarm condition described in Table 5-1.
• Active Defects field indicates what the local interface is receiving.
• Active Alarms field indicates what the upstream device is reporting.
Table 5-1 describes the Port status and Active defect errors the might appear in these fields, the cause of
the error, and a recommended solution.
Note Active alarms or defects keep an interface in the down and line protocol down state.
Table 5-1 Port Adapter and Active Defect Fields of the show controller Display
Indication (Severity) Error and Cause Recommendation
Good Signal None None
SLOS
1
(Critical) A link must see a certain number of digital bit
transitions (from 1 to 0 and 0 to 1) to ensure proper
synchronization. LOS is declared when no bit
transitions are detected on the incoming signal
(before descrambling) for 2.3 to 100
microseconds. The LOS defect is cleared after a
125 microsecond interval (one frame) during
which no LOS defect is detected.
1. Check the cable to make sure it is plugged in.
2. Verify that the local cable is not damaged. Look
for breaks or physical abnormalities.
3. Make sure that the remote end of the cable is
connected, undamaged and that the remote port is
configured properly.
4. Try a soft loopback with the loopback internal
command.
5. Try a hard loopback by connecting the transmit
to receive with a single cable.
SLOF
2
(Critical) The A1 and A2 bytes in the section overhead
provide frame alignment by using a particular bit
pattern. A receiving interface declares LOF after
detecting errors in the framing pattern for three
milliseconds. LOF is cleared when two
consecutive valid A1/A2 framing patterns are
received.
1. Check the cable to make sure it is plugged in
and is not damaged.
2. Ensure the framing format on the port matches
the format configured on the line.
LAIS
3
(Major) LAIS is sent by the section terminating equipment
(STE) to alert the downstream line terminating
equipment (LTE) that a LOS or LOF defect has
been detected on the incoming section. Upstream
STE generates line AIS to downstream LTE by
setting bits 6, 7, and 8 of the K2 byte to 111.
1. Verify that the remote configuration is correct.
2. Check the line status the remote end of the link.