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    Locating Loss of Signal Alarms

    Problem

    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.

    Solution

    To locate the LOS alarm, check the connection between the router port and the first SONET network element. In the example network in Figure 1, the X indicates that there is a connection problem between Repeater 2 and Router 2.

    Figure 1: Location of an LOS Alarm in a SONET Network

    Location of an LOS Alarm in a SONET
Network

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

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

    Sample Output

    user@router2> show interfaces so-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...]
    

    Meaning

    The sample output shows at the time the command was run, Router 2 continued to be in a LOS alarm state for around 51 seconds.

    Published: 2013-07-31