apt install asterisk -y
 

vi /etc/asterisk/sip.conf

[general]  
context=default  
allowoverlap=no  
udpbindaddr=0.0.0.0  
tcpenable=no  
tcpbindaddr=0.0.0.0  
transport=udp  
srvlookup=yes  
  
[1001]  
type=friend  
host=admin-cod.cod.ssa2026.region  
secret=secret 
  
[1002]  
type=friend  
host=cli-cod.cod.ssa2026.region  
secret=secret 
  
[2001]  
type=friend  
host=cli1-a.office.ssa2026.region  
secret=secret 
  
[2002]  
type=friend  
host=cli2-a.office.ssa2026.region  
secret=secret 

vi /etc/asterisk/extensions.conf

[general]  
static=yes  
writeprotect=no  
priorityjumping=no  
autofallthrough=yes  
clearglobalvars=no  
  
[default]  
exten => 1001,1,Dial(SIP/1001,10)  
exten => 1002,1,Dial(SIP/1002,10)
exten => 2001,1,Dial(SIP/2001,10)  
exten => 2002,1,Dial(SIP/2002,10)

Клиент

apt install linphone -y