Deploying an F5 Load Balancer in a PBX-SBC-Lync Topology

This article describes the steps necessary to configure the Sonus SBC 1000/2000 with an F5 Networks load balancer in a PBX-Sonus SBC 1000/2000-Microsoft Lync topology as illustrated below:

The elements used in this topology are as follows:

• 2x Microsoft Lync 2010 front end servers
• 1x F5 Networks hardware load balancer
• 1x Meridian PBX
• 1x Sonus SBC 1000/2000 Gateway

For more details regarding the F5 load balancer configuration and Lync integration, please review the F5 Hardware Loadbalancer (HWLB) Configuration section. You may also jump directly to the Sonus SBC 2000 Configuration and Call Flows sections.

F5 Hardware Loadbalancer (HWLB) Configuration

For the purpose of this article we assume that the F5 load balancer is installed and configured such that it is already successfully integrated with Lync 2010. For details regarding the configuration and integration of an F5 load balancer see the following F5 documents:

• BIG-IP Virtual Edition Setup Guide for VMware ESX or ESXi
• Deploying the BIG-IP LTM with Microsoft Lync Server 2010

Load Balancer Configuration Hints

1. Using the DNS Manager, verify that the Lync 2010 Enterprise Pool Alias is pointing (therefore resolving) to the IP address of the hardware Load balancer machine as shown below.

2. Verify that the VLAN interface used to communicate with the Lync server is tagged as indicted below.

3. Verify that the F5 MGMT IP address is configured to use the VLAN interface set in the previous step.

4. Verify that the VLAN interface Settings are configured as shown below.

5. Verify that Local Traffic > Nodes settings contain the Lync FE1, Lync FE2, and the virtual IP address of hardware load balancer machine as shown below.

6. Verify that the settings found in Local Traffic > Pools contain the pools that the F5 load balancer listens to Lync on defined port numbers for various services as shown below.

   NOTE: the details of pool creation is explained in Deploying the BIG-IP LTM with Microsoft Lync Server 2010as shown below.

7. Verify the virtual server making use of the pools created above has itself been created as shown below.

Sonus SBC 2000 Configuration

The Sonus SBC 1000/2000 configuration for deployment in this topology requires the following fields to be configured:

• Federated IP/FQDN: Pool FQDN in the IP/FQDN field
• Netmask: 255.255.255.255 in the Netmask field
  
  These fields allow the Sonus SBC 1000/2000 to receive SIP messages from the hardware load balancer HWLB. However, in order to receive/send SIP messages to/from Front End Servers, the Netmask field must be configured with a value of 255.255.255.0.

Call Flows

Using the Log Exchange utility, you can verify the F5 Hardware Load Balancer (HWLB) in action —

PSTN ph > Sonus SBC 1000/2000 > Lync client

The deployment in this article allows the following call flow in PSTN ph > Sonus SBC 1000/2000 > Lync client call direction.

LYNC client > Sonus SBC 1000/2000 > PSTN ph

The deployment in this article allows the following call flow in Lync client > Sonus SBC 1000/2000 > PSTN ph call direction.