SAMPLE SIP.conf file
[sip64]
type=peer
username=fiducia_ag
fromuser=fiducia_ag
authuser=fiducia_ag
secret=password
host=64.56.64.00
nat=no
canreinvite=yes
insecure=very
disallow=all
allow=g729
allow=ulaw
context=default
dtmfmode=rfc2833
[sip67]
type=peer
username=fiducia_ag
fromuser=fiducia_ag
authuser=fiducia_ag
secret=password
host=67.56.64.00
nat=no
canreinvite=yes
insecure=very
disallow=all
allow=g729
allow=ulaw
context=default
dtmfmode=rfc2833
Extension.conf :
exten => _9X.,1,AGI(agi://127.0.0.1:4577/call_log)
exten => _9X.,2,Dial(SIP/${EXTEN:1}@sip64||tTor)
exten => _9X.,3,Hangup()
exten => _8X.,1,AGI(agi://127.0.0.1:4577/call_log)
exten => _8X.,2,Dial(SIP/${EXTEN:1}@sip67||tTor)
exten => _8X.,3,Hangup()
If Dial Prefix is 8 , it will one SIP and if dial Prefix is 9, it will use another SIP.