The Nokia E75 has a SIP-based Voice over IP (VoIP) client built-in, meaning that the handset can make and receive calls over the Internet provided that the SIP PBX can be configured to support the device.

In this post I shall be using SIPtrix, the Asterisk-based Linux PBX server. 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.

To configure the SIP settings on the phone:

• On the handset, press the menu button. Select Control Panel and then Settings.
• Select Connection
• Select Destinations
• Select Access Point
• Select the option to Automatically check for available access points
• Select the desired wireless access point you wish to connect to
• Complete the required security settings as required
• Save the new access point to the Intranet Destination
• Return to the Connections menu and select SIP Settings
• Select Options → New SIP Profile → Use default profile
• Enter a name for the profile
• Set Service Profile to IETF
• Set Default Destination to Intranet
• 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 Control Panel and select Net Settings
If you don't see a menu icon for Advanced VoIP settings, you will need to download an additional component from the Nokia Forum web site:

http://www.forum.nokia.com/info/sw.nokia.com/id/105455c9-654b-427f-99c7-...

Registration is required for access to this web site.

This component is required to enable you to enable the "Internet Telephony" mode on the phone.
Once installed, you will see a new option in the Net Settings menu for Advanced VoIP Settings:

Select VoIP Services:

Select VoIP Settings --> Used SIP Profiles and enable the SIP Profile you created earlier.
Return to the Net Settings menu and select Provider sett.
Set Default Service to Yes.

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. 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:

Any calls made from the handset will appear to the recipient as coming from the DDI of that user’s desk phone. When placing a call from the phone, you will have the option of placing a Net Call: