Locate 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 14, the X indicates that there is a connection problem between Repeater 2 and Router 2.

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:

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 that Router 2 detected an LOS that lasted 51 seconds.