Configure Freepbx with Avaya PBX

Can anybody please advise on the below scenario,

We are trying to link our Elastix PBX server with Avaya PBX ( S8800 PBX) through SIP Trunk. We used the following settings to communicate with Avaya.

ASTERISK
Create a SIP Trunk like this.
Trunk Name : IPO
Peer Details :
context=from-internal
host=AVAYA’s IP
type=friend
qualify=yes
insecure=very
disallow=all
allow=alaw&ulaw&gsm

User Details :
type=user
host=AVAYA’s IP
context=from-internal
disallow=all
allow=gsm

Create Outbound Route.
Route Name : IPOffice
Dial Patterns : 3XXX (According your AVAYA’s extension format)
Trunk Squence : SIP/IPO
Under General Settings
Set “Allow Anonymous Inbound Sip Calls” to yes

Still not able to call, Shows “unreachable” in the Sip status.
And gives “circuit are busy rightnow” message while calling.

Please Assist !!

Thank you !!