Locate Loss of Signal Alarms

Purpose

A loss of signal (LOS) alarm indicates that there is a physical link problem with the connection to the router receive port from the neighboring SONET equipment transmit port.

Action

To locate the LOS alarm, check the connection between the router port and the first SONET network element. In the example network in Figure 14, the X indicates that there is a connection problem between Repeater2 and Router2.

Figure 14: Location of an LOS Alarm in a SONET Network

To display SONET alarms and errors, use the following JUNOS CLI operational mode command:

user@host> show interfaces so-fpc/pic/port extensive

Sample Output

user@router2> show interfaces s0-1/1/1 extensive

[... Output truncated...]

  Active alarms  : LOL, PLL, LOS

  Active defects : LOL, PLL, LOF, LOS, SEF, AIS-L, AIS-P, PLM-P

  SONET PHY:            Seconds        Count  State

    PLL Lock                 51            0  PLL Lock Error

    PHY Light                51            0  Light Missing

  SONET section:

    BIP-B1                    0            0

    SEF                      51            0  Defect Active

    LOS                      51            0  Defect Active

    LOF                      51            0  Defect Active

[...Output truncated...]

What It Means

The sample output shows that Router2 detected an LOS that lasted 51 seconds.