SIP Trunk Configuration
-----------------------

Peer details:

host=sipproxy.voipgrid.nl
username=<accountid>
fromuser=<accountid>
secret=<password>
type=friend
sendrpid=yes
trustrpid=yes
insecure=invite
disallow=all
allow=alaw
nat=yes

User details:

EMPTY

Register string:

EMPTY

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Configuration in client.voys.nl dashboard for VOIP Trunk
--------------------------------------------------------

Use trunk supplied CLI information -> ticked

Advanced (SIP) Settings:

Static Hostname: <your ip address>
NAT rport -> ticked
Assume NAT IP -> ticked
CLI header: Remote-Party-ID SIP Header


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

I didn't change any of the other settings in the client.voys.nl dashboard.

Not all options may be needed, this is my first time dabbling with VOIP/Asterisk, but this is how it works for me.

Elastix server is behind a firewall with port 5060 and 10010-11000 (all UDP) forwarded.

help.voys.nl doesn't mention anything about the insecure option, without it the elastix server would not accept any incoming calls.