sla.conf
[line1]
type=trunk
trunk => Zap/1


[525]
type => station
device => SIP/525
trunk => line1
context => internal

extensions.conf
[line1]
exten => s,1,SLATrunk(line1)

[sla_stations]
exten => 525,1,SLAStation(525)
exten => 525_line1,1,SLAStation(525_line1)
exten => 525_line1,hint,SLA:525_line1



asterisk*CLI> sla show trunks
asterisk*CLI> 
=============================================================
=== Configured SLA Trunks ===================================
=============================================================
===
=============================================================

asterisk*CLI> sla show stations
asterisk*CLI> 
=============================================================
=== Configured SLA Stations =================================
=============================================================
===
============================================================