It's actually pretty simple... (I assume you know how to add a new SIP user in general)
Set the public facing IP of the router in System - IP Settings - System NAT IP Address and in System - Device annd Feature Codes - IP Connections - P6000 (base) - NAT IP Address
In the SIP Peers Phone Profile Configuration leave everything default except set:
Call Congfiguration: 2
Maximum Number of Calls: 2
Supports Display Updates: Yes
Supports Ad Hoc Conferencing: Yes
DTMF Decoding Payload: 101
Authentication:
Enable In-bound Auth: Yes
Inbound Auth Username: sipuserxxx (a unique username, if it's x125, we often use sipuser125)
Inbound Auth Pass: xxxxxxxxxxxx (complex SIP password)
Use P-Asserted-Identity: Yes
MWI: Accept MWI - Yes
NAT Settings: NAT Address Type: NAT
In the firewall, disable SIP ALG and set port forward to the following:
SIP: 5060/UDP from Any to MiVO 250 IP
RTP: 6004-7039/UDP from Any to MiVO 250 IP
In the user, change the NAT type from Native to NAT
In Bria setup for the server, make the following changes:
Service Label: (Account name you define)
Domain: (Public IP of firewall)
Port: Auto (or 5060)
Username/Call Extension: xxx (user extension)
Authorization Username: sipuserxxx (username on SIP Profile above)
SIP/Voice Password: xxxxxxxxxxxx (use a complex password from SIP profile above)
Call Display: (blank)
Register with domain and receive calls: Yes
SIP Proxy: (blank)
Transport: UDP
SRTP: No/Disabled
Registration Time: 300
RPORT: Enabled
Keep Alive: Enabled
Voicemail Number: 2500 (Ext of VM application)
Firewall Method: None
(everything else leave unchanged)
In the mobile app after installing and signing in, go to Settings - Accounts - (Account Name)
Use Push Notifications: ON
Push Registration Mode: Single Device Takeover
NAT Emulation: OFF
(Do not change anything else)