Locate T1 Alarms and Errors
This section includes the following information to assist you when troubleshooting T1 interfaces:
Checklist for T1 Alarms and Errors
To check T1 alarms and errors.
Table 1 provides the links and commands for checking T1 alarms and errors.
Table 1: Checklist for T1 Alarms and Errors
Command or Action
|Display T1 Alarms and Errors|
show interfaces t1-fpc/pic/port extensive
|Locate Most Common T1 Alarms and Errors|
Check the connection between the router port and the first T1 network element.
Check the T1 network element connected to the T1 interface.
Check the cable between the T1 interface and the directly connected T1 network element.
Display T1 Alarms and Errors
To display T1 alarms and errors, use the following Junos OS command-line interface (CLI) operational mode command:
user@host> show interfaces t1-1/1/0 extensive
Physical interface: t1-1/1/0, Enabled, Physical link is Down Interface index: 24, SNMP ifIndex: 20, Generation: 27 Link-level type: PPP, MTU: 1504, Clocking: Internal, Speed: T1, Loopback: None, FCS: 16, Framing: ESF Device flags : Present Running Down Interface flags: Hardware-Down Point-To-Point SNMP-Traps Link flags : Keepalives Hold-times : Up 0 ms, Down 0 ms Last flapped : 2002-01-01 00:00:35 UTC (00:01:00 ago) Statistics last cleared: 2002-01-01 00:01:03 UTC (00:00:32 ago) Traffic statistics: Input bytes : 0 0 bps Output bytes : 0 0 bps Input packets: 0 0 pps Output packets: 0 0 pps Input errors: Errors: 0, Drops: 0, Framing errors: 0, Policed discards: 0, L3 incompletes: 0, L2 channel errors: 0, L2 mismatch timeouts: 0, HS link CRC errors: 0, SRAM errors: 0 Output errors: Carrier transitions: 0, Errors: 0, Drops: 0, Aged packets: 0 DS1 alarms : LOF, LOS DS1 defects : LOF, LOS T1 media: Seconds Count State SEF 32 0 Defect Active BEE 0 0 OK AIS 0 0 OK LOF 32 0 Defect Active LOS 32 0 Defect Active YELLOW 0 0 OK BPV 0 0 EXZ 0 0 LCV 0 0 PCV 32 10667 CS 0 0 LES 0 ES 32 SES 32 SEFS 32 BES 0 UAS 32 HDLC configuration: Policing bucket: Disabled Shaping bucket : Disabled Giant threshold: 1514, Runt threshold: 3 Timeslots : All active Line encoding: B8ZS, Byte encoding: Nx64K, Data inversion: Disabled Buildout : 0 to 132 feet DS1 BERT configuration: BERT time period: 10 seconds, Elapsed: 0 seconds Induced Error rate: 10e-0, Algorithm: Unknown (0) Packet Forwarding Engine configuration: Destination slot: 1, PLP byte: 1 (0x00) CoS transmit queue Bandwidth Buffer Priority Limit % bps % bytes 0 best-effort 0 0 0 0 low none 1 expedited-forwarding 0 0 0 0 low none 2 assured-forwarding 0 0 0 0 low none 3 network-control 0 0 0 0 low none
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 seconds plus or minus 0.5 seconds, an alarm is declared.
Notification messages are logged at the alarm level. Depending on the type of T1 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 T1 media-specific alarms or defects that can render the interface unable to pass packets.
Table 2: T1 Interface Alarms and Error Definitions
T1 Alarm or Error
Severely errored frame
Block error event
Alarm indication signal (blue alarm)
Loss of frame
Loss of signal
Line code violation
Path code violation
Line errored seconds
Severely errored seconds
Severely errored frame seconds
Bursty errored seconds
Locate Most Common T1 Alarms and Errors
To locate common alarms and errors, follow these steps:
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 T1 interface.
To locate the LOS or LOF alarm, check the connection between the router port and the first T1 network element. In the example network in Figure 1, the X indicates that there is a connection problem between Router2 and the nearest T1 network element.
Tx represents the transmit port and Rx represents the receive port.
user@router2> show interfaces t1-1/1/1 extensive
[... Output truncated...] DS1 alarms : LOF, LOS DS1 defects : LOF, LOS T1 media : Seconds Count State SEF 32 0 Defect Active BEE 0 0 OK AIS 0 0 OK LOF 32 0 Defect Active LOS 32 0 Defect Active YELLOW 0 0 OK BPV 0 0 EXZ 0 0 LCV 0 0 PCV 32 10667 CS 0 0 LES 0 ES 32 SES 32 SEFS 32 BES 0 UAS 32 [...Output truncated...]
The sample output shows that Router 2 (Rx) detected a cumulative LOS and LOF alarm for 32 seconds.
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 T1 network element connected to the T1 interface.
To locate the AIS alarm, have the carrier check the T1 network element connected to the T1 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 T1 network.
In Figure 2, the X indicates that there is an LOS or LOF alarm between the repeater and the Tx T1 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 T1 network element connected to the T1 interface has a problem with the signal it is receiving from the T1 interface.
To locate the yellow alarm, check the cable between the T1 interface and the directly connected T1 network element.
All diagnostics are from the perspective of Router 2. Figure 3 illustrates the location of a yellow alarm in a T1 network.
In Figure 3, the T1 multiplexer detects an LOS or LOF alarm on its connection from Router 2 and sends a yellow (YLW) alarm to Router 2.