Any SIP phone that has achieved OnSIP certification has also received a knowledge base article for phone configuration with the OnSIP. These instructions are for generic SIP phones and phones that have not been through our lab yet. 

Gather information for each user

For most SIP devices, there are only five fields which must be entered for the SIP device to register with OnSIP. Those fields are:

• "SIP Address" (Address of Record)
• "SIP Password"
• "Auth Username"
• "Username"
• "Domain"
• "Outbound Proxy"

Each SIP device may call these fields something different. Here are some examples:

• "SIP Address" may be called => address
• "SIP Password" may be called => auth password or just password
• "Auth Username" may be called => authorization username or auth user id
• "Username" may be called => user, phone number or user id
• "Domain" may be called => proxy, domain
• "Outbound Proxy" may be called => outbound proxy, proxy or registrar server or SIP server. The outbound proxy is always sip.onsip.com.

In the app.onsip.com under the Administrators tab, you will find the SIP settings in the "Phone Settings" tab under each user.

Specifications:

Username - Cannot start with a number.  Cannot be all numbers.  Cannot be more than 32 characters long.  A username is a non-numeric address and must begin with a letter and may contain only letters, numbers, periods, underscores, and dashes or a combination thereof.

Domain - a domain must contain no more than 60 characters and must be a standard domain  lowercase letters, numbers, and dashes.

Disable NAT settings on the SIP phone

It is important that all NAT settings are turned off. Disable any STUN or ICE settings. If you have an option to "Use Internal IP Address" or something to that effect, do it. We need the phone to report its internal IP address to OnSIP, and we will capture the external IP address from the actual packet headers.
More recommendations about NAT. 

Set your outbound proxy on the SIP phone

Your device provides support for using an "outbound proxy" and it should be set. However, in many cases this setting is not in the same configuration section as the user settings. Nonetheless, set it to:

sip.onsip.com

More recommendations about outbound proxy.

Confirm that your SIP phone is registered

In the portal, click on the “Users”. You will see an "online" notation next to each user with a registered phone.