Configuring and Troubleshooting Dual NICs for Cisco Unity

Document ID: 46266

Contents

Introduction
Problem
Solution
Tools Information
Related Information

Introduction

This document describes how to properly configure Cisco Unity to work with two Network Interface Cards (NICs) when integrating Cisco Unity with a CallManager. Voice messaging will not work as expected if it is not properly configured.

Problem

Many enterprise customers who source their own hardware will purchase a platform that has two NICs on it. If these NICs are not configured properly, voice messaging will not work correctly and you will experience problems such as one-way audio or Message Waiting Indicator (MWI) malfunction. This document indicates the supported configuration for dual NICs.

• This applies to all versions of Cisco Unity integrated with a Cisco CallManager.

Problems with Active-active Load Sharing Configuration

Configuring dual NICs for active-active load sharing, meaning that 50 percent of the traffic is handled by each NIC, could lead to one-way audio and MWI problems. This setup is currently not supported on a Cisco Unity server .

How Active-active Load Sharing can Result in One-way Audio

The following is a cause of dual NICs resulting in one-way audio during call processing with a Cisco CallManager integration, using Skinny protocol:

1. With a Skinny integration, you have to send your IP address to the other side of the call.
2. You determine your IP address by repeating through the NICs and returning the IP address of the first NIC you find.
3. In a dual NIC configuration, you may choose the IP address of the wrong NIC causing the one-way audio issue.

Solution

There are two supported configurations when installing Cisco Unity on a platform with two NICs:

1. Disable one of the NICs.
2. Configure the NICs in an active-passive manner.

Active-passive Fault Tolerance

Cisco Unity does support using dual NICs configured in an active-passive manner for fault tolerance. In this NIC configuration, the primary (active) NIC handles 100 percent of the traffic. Only in the event that it goes down, does the secondary NIC become active and would handle 100 percent of the traffic. Therefore, only one IP address and one network (no subnets with each NIC on a different subnet) is supported.

Related Information

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