Backup SIP calling with Teams Phones (Poly CCX)

The latest release of firmware version 7.2.1 allows Poly CCX native Teams phones to have a secondary SIP registration with a standards-based VOIP call server. The Teams account signed in on the phone still remains the primary line for incoming/outgoing calls, while the secondary SIP registration will allow PSTN calls in the event that the Teams connection becomes unavailable. This is useful for disaster recovery scenarios where the corp WAN link is down and the device is no longer able to communicate with Teams. In this case with the secondary SIP registration to a local PBX with PSTN Trunks, users can manually switch to the SIP registered line and continue to make PSTN calls. Note that this is manual failover, not automatic . The blog post describes the steps to enable and deploy this feature. Do note that this feature only works with CCX400/500 with HW Rev K or higher and CCX600.

We begin with a Poly CCX600 native Teams phone that's in Teams base profile and already signed into a user account assigned with E5 licenses and PSTN connectivity via Direct Routing. By default, hybrid SIP registration is disabled and we can edit an xml config file to enable this feature. The config file simply contains the necessary parameters as shown below:

<?xml version="1.0" encoding="utf-8" standalone="yes"?>
<!--Description: Enables Teams Call App switching in Generic BP -->
<polycomConfig>
  <teams.callappswitching
    apps.android.appSwitcher.enabled="1"
    apps.android.navBar.enabled="1"
    apps.android.statusBar.UCS.enabled="1"
    apps.android.appSwitcher.MSTeams.enabled="1"
    apps.android.primaryApp="MSTeams"
    apps.android.navBar.enabled="1"
    voIpProt.SIP.enable="1" >
  </teams.callappswitching>
</polycomConfig>

Save the above file as 'enable_app_switcher.cfg' in plain text format and upload it to the phone via your provisioning server or directly using the phone's web admin UI. For this blog post we will simply use the phone's web admin UI as shown below:

After clicking on the "Import" button, the phone will take in the config file and reboot. After this, we can start using the second SIP registration feature. The picture below on the left shows the Teams phone home page while the picture below on the right shows the phone menu when a user swipes down the screen from the top revealing 2 icons:

Clicking between the Poly and Teams icons will allow switching between Teams and the backup SIP line. The picture below shows the backup phone's interface when we press the Poly icon:

At this stage, we cannot use the secondary SIP line as we need to configure it on the phone first. In this lab we have a SIP server at IP 192.168.0.181 and created a SIP user "100" with extension of "100" and password of "100". In this case, we can add the following lines in red to the config file and import into the phone as before:

<?xml version="1.0" encoding="utf-8" standalone="yes"?>
<!--Description: Enables Teams Call App switching in Generic BP -->
<polycomConfig>
  <teams.callappswitching
    apps.android.appSwitcher.enabled="1"
    apps.android.navBar.enabled="1"
    apps.android.statusBar.UCS.enabled="1"
    apps.android.appSwitcher.MSTeams.enabled="1"
    apps.android.primaryApp="MSTeams"
    apps.android.navBar.enabled="1"
    voIpProt.SIP.enable="1"
    reg.1.server.1.address="192.168.0.181"
    reg.1.server.1.expires="300"
    reg.1.address="100@myvoipapp.com"
    reg.1.auth.password="100"
    reg.1.auth.userId="100"
    reg.1.label="SIP100"
    reg.1.displayName="SIP100"
    reg.1.lineKeys="1"
    reg.1.ringType="ringer2" >
  </teams.callappswitching>
</polycomConfig>

As shown in the above picture, the SIP line is now registered to our SIP server allowing us to make PSTN or PBX calls. Note that this screen will on remain for about 30secs if there is no user input. After that it will revert back to the original Teams interface as it should be under normal network conditions. Hope this post will be useful for anyone who needs to configure a secondary SIP line on Teams phones for backup or failover purposes. Last but not least, we can also the the app switch icon on the Teams home screen to access the SIP line: