HOWTO make Asterisk <-- TALK TO --> SipX (how to make asterisk talk to sipx)
/etc/hosts
Do not remove the following line, or various programs
that require network functionality will fail.
127.0.0.1		localhost.localdomain localhost
172.16.15.27		sea-na-pbx2317.na.eedinc.net na.eedinc.net    /* this is the Asterisk Server
172.16.15.25         sea-na-pbx3251.na.eedinc.net na.eedinc.net   /* this is the SipX server
===========================================
sip.conf
;[general] section contains the channel settings
;and default options for all users and peers defined here within sip.conf
[general]
allowguest=yes
context=default
port=5060                ; Asterisk uses port 5060 for SIP signalling
bindport=5060
bindaddr=0.0.0.0         ; Tells Asterisk to listen on all interfaces
srvlookup=yes            ; Disable or Enable DNS SRV lookups
disallow=all
allow=ulaw
canredirect=no
careinvite=yes
dtmfmode=rfc2833
host=172.16.15.25
nat=no
[sipx3251]
;
;    Channel used to call SipX Corp
;
type=friend
context=outgoing
host=sea-na-pbx3251.na.eedinc.net
insecure=invite
disallow=all
allow=ulaw
[7777]
type=friend              ; Defined as both user and peer
secret=7777              ; password
username=7777
qualify=yes              ; Qualify peer is no more than 2000 ms away
nat=no                   ; This phone is not natted
host=dynamic             ; Phone uses DHCP
defaultip=192.168.6.103  ; Use the ip given in DHCP whene VPNed in.
canreinvite=yes          ; Asterisk by default tries to redirect
context=default          ; the internal context controls what we can do
dtmfmode=rfc2833         ; sipx likes that
extensions.conf
[general]
static=yes
writeprotect=yes
[internal]
include => outgoing
exten => 7777,1,Dial(Sip/7777,20)
exten => 7777,2,Dial(Sip/7777@sea-na-pbx2317.na.eedinc.net,20,t)
exten => 7777,3,Hangup()
[incoming]
exten => 7777,1,Dial(SIP/7777,20)
exten => 7777,2,Dial(SIP/7777@sea-na-pbx2317.na.eedinc.net,20,t)
exten => 7777,3,Hangup()
[outgoing]
;
;    Call a SipX extension
;
exten => 2218,1,Dial(SIP/sipx3251/${EXTEN})
;
[default]
;
include => internal
include => outgoing
****    WARNING    ****    WARNING    ****    WARNING    ****
The above mentioned configuration is very basic and just an example of how I was able to get my Asterisk box to talk to a SipX box. This is not a recomendation for how to define your channels and dial plan up for a finalized operating environment.