When the gateway in a Lync - SBC Edge - PBX topology fails, a Lync client will lose its connectivity with PSTN. The use of a back-up or fail-over gateway becomes highly desirable in order to maintain connectivity between Lync and PSTN.

This article describes the steps necessary to configure an additional SBC Edge (SBC) as a fail-over gateway along with the necessary Lync topology configuration bits. For the purpose of this article, it is assumed that PBX – SBC (Primary) – Microsoft Lync 2010 configuration is already in place with MTLS/SRTP as the SIP Transport as shown in the diagram below.

 

Topology

Overview

This is a two-part process; in the first part of the process, we use the Lync 2010 Setup Wizard on two different SBCs to point each of them at the same Lync Pool. In the second part, we do the complementary action on the Lync side by specifying both of the SBCs as PSTN Gateways using the Lync 2010 Topology Builder.

SBC Configuration

For this exercise, the following are the identities of the pool and SBC devices:

  • Lync Pool Name: cspool.mxlync.com
  • Primary SBC: testux212.mslync.com
  • Secondary SBC: testux226.mslync.com

Lync 2010 Setup

 

Primary SBC Configuration

After successfully running the wizard, a primary SBC is configured for Lync 2010 Interoperability as shown below.

Lync Setup - Mediation Servers

 

Secondary SBC Configuration

After successfully running the wizard, a secondary SBC is configured for Lync 2010 Interoperability as shown below.

msLync - Mediation Servers

LYNC Topology Configuration

To add the secondary SBC Node into the Lync Topology, please follow these steps:

Defining the Gateway

To define the gateway:

  1. Use Remote Desktop to connect to the Lync Front End Server.
  2. Launch the Topology Builder.
  3. In the left pane, right-click on PSTN gateways.

  4. Select Define New Gatewayto add the secondary SBC gateway as shown below.

    Define Gateway

     

     

Associating the Gateway with a Mediation Server

To associate the gateway:

  1. Use Remote Desktop to connect to the Lync Front End Server.
  2. Launch the Topology Builder.
  3. In the left pane select Mediation pools > relevant pool.
  4. Right-click, then select Edit to open its properties.
  5. Select the newly added SBC gateway from the list.

  6. Click Add...to associate it with the Mediation Server as shown below.

    Associate with Mediation Server

  7. Use Remote Desktop to connect to the Lync Front End Server.
  8. Launch the Topology Builder.
  9. Right-click on Lync Server 2010 in left pane.

  10. Select Publish Topology...as shown below.

    Publish Topology

Configuring the LYNC Voice Routing

To configure voice routing:

  1. Open the LYNC Server 2010configuration page:
    1. Enter the URL of the Front-End pool (https://<fqdn of the front end pool>/cscp).
  2. Click Voice Routing in the left pane.
  3. Click Voice Policy in the right pane.

  4. Double-click the relevant policy_ in the list.

    Select Relevant Policy

     

     

  5. Double click the relevant PSTN usage record.

    Select Relevant PSTN Usage Record

     

     

  6. Double click on the Route entry.

    Select Route Entry

  7. Add the secondary SBC gateway into Associated Gateways list

    Add Secondary Sonus SBC 1000/2000 Gateway

  8. Click OK, OK, and OK to exit the Voice Policy configuration.