SERVER 1
#######################################
===================
sip.conf
===================
[general]
port=5060
bindaddr=0.0.0.0
context=other

[301]
type=friend
context=phone
username=pcserver
secret=123
host=dynamic

[asterisk2]
type=friend
context=phone
host=192.168.1.11
insecure=invite
allow=all

===================
extensions.conf
===================

[other]
[phone]
exten => 301,1,Dial(SIP/301)
exten => 301,n,Hangup()

exten => _2XX,1,Dial(SIP/${EXTEN}@asterisk2)
exten => _2XX,n,Hangup() => exten => 301,1,Dial(SIP/301)

===========================================================================

SERVER 2
#####################
===================
sip.conf
===================
[general]
port=5060
bindaddr=0.0.0.0
context=other

[201]
type=friend
context=phone
username=nanank
secret=123
host=dynamic

[asterisk1]
type=friend
context=phone
host=192.168.1.13
insecure=invite
allow=all

===================
extensions.conf
===================

[other]
[phone]
exten => 201,1,Dial(SIP/201)
exten => 201,n,Hangup()

exten => _2XX,1,Dial(SIP/${EXTEN}@asterisk1)
exten => _2XX,n,Hangup() => exten => 201,1,Dial(SIP/201)