Locate T3 Alarms and Errors
This section includes the following information to assist you when troubleshooting T3 interfaces:
Checklist of Common T3 Alarms and Errors
To check T3 alarms and errors,
Table 1 provides the links and commands for checking T3 alarms and errors.
Table 1: Checklist of Common T3 Alarms and Errors
Command or Action
|Display T3 Alarms and Errors|
show interfaces t3-fpc/pic/port extensive
|Locate Most Common T3 Alarms and Errors|
Check the connection between the router port and the first T3 network element.
Check the T3 network element connected to the T3 interface.
Check the cable between the T3 interface and the directly connected T3 network element.
Check that the line is provisioned for service.
T3 is a general term used to refer to the transmission of 44.736-Mbps digital circuits over any media. T3 can be transported over copper, fiber, or radio. DS3 is the term for the electrical signal found at the metallic interface for this circuit where most of the testing is performed.
Display T3 Alarms and Errors
To display T3 alarms and errors, use the following Junos OS command-line interface (CLI) operational mode command:
user@host> show interfaces t3-1/0/0 extensive
Physical interface: t3-1/0/0, Enabled, Physical link is Down Interface index: 9, SNMP ifIndex: 10 Link-level type: Cisco-HDLC, MTU: 4474, Clocking: Internal Speed: T3, Loopback: None, CRC: 16, Mode: C/Bit parity Device flags : Present Running Down Interface flags: Hardware-Down Link-Layer-Down Point-To-Point SNMP-Traps Link flags : Keepalives Keepalive statistics: Input : 116 (last seen 00:02:59 ago) Output: 187 (last seen 00:00:09 ago) Statistics last cleared: Never Traffic statistics: Input bytes : 2552 0 bps Output bytes : 3703 0 bps Input packets: 116 0 pps Output packets: 161 0 pps Input errors : Errors: 0, Drops: 0, Framing errors: 229, Policed discards: 1 L3 incompletes: 0, L2 channel errors: 0, L2 mismatch timeouts: 0 SRAM errors: 0, HS link CRC errors: 0 Output errors : Carrier transitions: 4, Errors: 0, Drops: 0, Aged packets: 0 Active alarms : LOF, LOS - DS-3 active alarms and defects Active defects : LOF, LOS DS3 Media: Seconds Count State - T3 media-specific errors PLL Lock 0 0 OK Reframing 273 2 Defect Active AIS 0 0 OK LOF 273 2 Defect Active LOS 273 2 Defect Active IDLE 0 0 OK YELLOW 0 0 OK BPV 0 0 EXZ 0 0 LCV 275 18022125 PCV 0 0 CCV 0 0 LES 275 PES 273 PSES 273 CES 273 CSES 273 SEFS 273 UAS 277 [...Output truncated...]
The sample output shows active alarms and active defects. When a major error (such as an alarm indication signal [AIS]) is seen for a few consecutive frames, a defect is declared within 1 second from detection. At the defect level, the interface is taken down and routing protocols are immediately notified (this is the default). In most cases, when a defect persists for 2.5 second plus or minus 0.5 seconds, an alarm is declared.
Notification messages are logged at the alarm level. Depending on the type of T3 alarm, you can configure the craft panel to display the red or yellow alarm LED and simultaneously have the alarm relay activate a physically connected device (such as a bell).
Table 2 lists the T3 media-specific alarms or errors that can render the interface unable to pass packets.
Table 2: T3 Interface Error Counter Definitions
T3 Alarm or Error
Alarm indication signal
Idle code detected
Line code violation
Loss of signal
Loss of frame
Remote defect indication (yellow alarm)
Phase locked loop
Locate Most Common T3 Alarms and Errors
The following alarms and errors are described in this chapter:
Locate Loss of Signal and Loss of Frame Alarms
Description: A loss of signal (LOS) or loss of frame (LOF) alarm indicates that a signal could not be detected at the T3 interface.
To locate the LOS or LOF alarm, check the connection between the router port and the first T3 network element. In the example network in Figure 1, the X indicates that there is a connection problem between Router 2 and the nearest T3 network element.
Tx represents the transmit port and Rx represents the receive port.
user@router2> show interfaces t3-1/1/1 extensive
[... Output truncated...] Active alarms : LOF, LOS Active defects : LOF, LOS DS3 Media: Seconds Count State PLL Lock 0 0 OK Reframing 273 2 Defect Active AIS 0 0 OK LOF 273 2 Defect Active LOS 273 2 Defect Active [...Output truncated...]
The sample output shows that Router 2 (Rx) detected a cumulative LOS and LOF for 273 seconds. The defect was declared twice during that time.
Locate Alarm Indication Signal Alarms
Description: An alarm indication signal (AIS) is a valid framed signal with payload containing a repeating 1010 pattern. An AIS alarm indicates a problem with the line upstream from the T3 network element connected to the T3 interface.
To locate the AIS alarm, have the carrier check the T3 network element connected to the T3 interface and trace the problem.
All diagnostics are from the perspective of Router 2 (the Juniper Networks router). Figure 2 illustrates the location of an AIS alarm in a T3 network.
In Figure 2, the X indicates that there is an LOS or LOF alarm between the repeater and the Tx T3 multiplexer. An AIS alarm is sent from the repeater to Router 2.
Locate an Incoming Yellow Alarm
Description: An incoming yellow alarm indicates that the T3 network element connected to the T3 interface has a problem with the signal it is receiving from the T3 interface.
To locate the yellow alarm, check the cable between the T3 interface and the directly connected T3 network element.
All diagnostics are from the perspective of Router 2. Figure 3 illustrates the location of a yellow alarm in a T3 network.
The T3 multiplexer detects an LOS or LOF on its connection from Router 2 and sends a yellow (YLW) alarm to Router 2.
Locate IDLE on a T3 Interface
Description: The T3 (DS3) IDLE signal is a validly framed DS3 signal with a payload consisting of a repeated 1100 signal. IDLE indicates that the line has not been provisioned for service.
Have the carrier make sure that the line is provisioned for service.
user@router2> show interfaces t3-1/1/0
Physical interface: t3-1/1/0, Enabled, Physical link is Down Interface index: 13, SNMP ifIndex: 21 Link-level type: PPP, MTU: 4474, Clocking: Internal Speed: T3, Loopback: None, CRC: 16, Mode: C/Bit parity Device flags : Present Running Down Interface flags: Hardware-Down Point-To-Point SNMP-Traps Link flags : Keepalives Input rate : 0 bps (0 pps), Output rate: 0 bps (0 pps) Active alarms : IDLE Active defects : IDLE