Before the Nokia E series handsets can be used as remote extensions, there are a number of pre-requisites that need to be satisfied on the server:

The SIPtrix server must have a ‘real world’, ‘routable’, ‘public’, or ‘Internet-facing’ IP address that is available from the Internet. Without this, no remote connectivity will be possible.
If the SIPtix server is behind a firewall, then UDP port 5060 should be allowed through to the server from the Internet, for SIP signalling traffic. The UDP port range 10000 to 20000 must also be allowed through for RTP traffic (the ‘media’ of the telephone conversation).

The SIPtrix server must also be ‘made aware’ of its own external IP address as well as the local network on which it sits:
Log into the admin interface for the server via the web interface and browse to Tools → Config Edit. Locate the ‘sip_nat.conf’ file and add the following lines:

nat=yes
externip=81.138.13.178
localnet=10.0.0.0/255.255.255.0

(you will need to substitute the above IP details for the configuration of your own external and internal network addressing scheme).

Once these pre-requisites have been satisfied, you must now create an extension on the system for the phone to register as.

Within the admin interface, add an extension in the correct number range (1xx would be suitable for remote extensions to identify them as such and separate them from the 2xx internal extensions).
Set the Outbound CID number to match that of the person’s desk extension.
Set the secret to password or something suitable.
Set the NAT field to ‘yes’
Disable voicemail.

(Optional)
Create a ring group and add the person’s desk extension and the E series handset as members. Set the Inbound route for the person’s DDI to point to the ring group.
Set the ring strategy to ring all.

Submit and Apply the changes.

Now we are ready to configure the Nokia handset.

If the wireless access point the handset is connecting to is locked down by MAC address, then it will need to be configured to allow the handset to connect to it.

MAC stands for Media Access Control. A MAC address is a unique hexadecimal address that is assigned to all networking equipment. To ascertain the MAC address of the Nokia handset, issue the following code on the handset keypad itself:

*#62209526#

The MAC address will be returned:

On the handset, press the menu button. Select Tools and then Settings.
Select Connection
Select Access Points
Select Options and then New Access Point
Enter a name for the connection, the name of the wireless access point would be a sensible name to use
Set the Data Bearer to Wireless LAN
Select the WLAN network name field and select the option to Search for networks. Select the desired wireless network. If the access point is not set to broadcast its SSID, then type in the SSID manually.
Set the Network Status to Public
Set the WLAN network mode to Infrastructure
Set the WLAN security mode as required. If you are using WEP or WPA encryption then select the correct type. Then select WLAN security settings and enter the correct key to be used.

Return to the Connections menu and select SIP Settings
Select Options → New SIP Profile → Use default profile
Enter a name for the profile, again the name of the access point would be sensible.

Set Service Profile to IETF
Set Default Access to the Access Point you configured earlier
Set Public user name to sip:1xx@10.0.0.100 (where 1xx is the 3-digit extension, and the IP address is the internal IP address of the SIPtrix server)
Set Use compression to No
Set Registration to Always on
Set Use security to No

Select Proxy Server

Set Proxy server address to sip:81.138.13.178 (where the IP address is the external IP address of the SIPtrix server)
Set Realm to asterisk
Set User name to 1xx (where 1xx is the 3-digit extension)
Set Password to (the password you defined in the properties of the extension within the SIPtrix admin interface)
Set Allow loose routing to Yes
Set Transport type to UDP
Set Port to 5060

Select Registrar Server

Set Registrar server addr. to sip:asterisk
Set Realm to None
Set User name to None
Set Password to None
Set Transport type to UDP
Set Port to 5060

Return to the Connection menu
Select Internet tel. settings
Create a new profile
Enter a name for the profile, the name of the access point will do
Set the SIP profile to name of the profile you created earlier

Return to the Settings menu
Select Phone and then Call
Set Default call type to Internet Call

Return to the home screen
Power the handset off and on again.

When the handset powers back on, it will register with the wireless access point and then with the remote SIPtrix server. Any calls made from the handset will appear to the recipient as coming from the DDI of that user’s desk phone.

You will know if the handset is registered in Internet Call mode, as there will be an icon of a handset and a globe in the top right hand corner of the display: