Create or Configure an Availability Group Listener (SQL Server)

To determine whether a listener already exists for the availability group

• View Availability Group Listener Properties (SQL Server)

Note
If a listener already exists and you want to create an additional listener, see To Create An Additional Listener for an Availability Group (Optional), later in this topic.

• You can create only one listener per availability group through SQL Server. Typically, each availability group requires only one listener. However, some customer scenarios require multiple listeners for one availability group. After creating a listener through SQL Server, you can use Windows PowerShell for failover clusters or the WSFC Failover Cluster Manager to create additional listeners. For more information, see To Create An Additional Listener for an Availability Group (Optional), later in this topic.

Using a static IP address is recommended, although not required, for multiple subnet configurations.

• You must be connected to the server instance that hosts the primary replica.

• If you are setting up an availability group listener across multiple subnets and plan to use static IP addresses, you need to get the static IP address of every subnet that hosts an availability replica for the availability group for which you are creating the listener. Usually, you will need to ask your network administrators for the static IP addresses.

Important
Before you create your first listener, we strongly recommend that you read Prerequisites, Restrictions, and Recommendations for AlwaysOn Client Connectivity (SQL Server).

Each availability group listener requires a DNS host name that is unique in the domain and in NetBIOS. The DNS name is a string value. This name can contain only alphanumeric characters, dashes (-), and hyphens (_), in any order. DNS host names are case insensitive. The maximum length is 63 characters, however, in SQL Server Management Studio, the maximum length you can specify is 15 characters.

We recommend that you specify a meaningful string. For example, for an availability group named AG1, a meaningful DNS host name would be ag1-listener.

Important

NetBIOS recognizes only the first 15 chars in the dns_name. If you have two WSFC clusters that are controlled by the same Active Directory and you try to create availability group listeners in both of clusters using names with more than 15 characters and an identical 15 character prefix, you will get an error reporting that the Virtual Network Name resource could not be brought online. For information about prefix naming rules for DNS names, see Assigning Domain Names.

Permissions	Link
The cluster object name (CNO) of WSFC cluster that is hosting the availability group must have Create Computer objects permission: If the Create Cluster wizard created this WSFC cluster while running in a domain user account with Create Computer objects permission, cluster object name (CNO) of this WSFC cluster already has this permission. If the account that ran the Create Cluster wizard did not have Create Computer objects permission, give the WSFC cluster name to your domain administrators and ask them to grant this permission to the cluster object name (CNO) of the WSFC cluster. Note In some organizations, the security policy prohibits granting Create Computer objects permission to individual user accounts.	Steps for configuring the account for the person who installs the cluster in Failover Cluster Step-by-Step Guide: Configuring Accounts in Active Directory Steps for prestaging the cluster name account in Failover Cluster Step-by-Step Guide: Configuring Accounts in Active Directory
If your organization requires that you prestage the computer account for a listener virtual network name, you will need membership in the Account Operator group or your domain administrator's assistance. Tip Generally, it is simplest not to prestage the computer account for a listener virtual network name. If you can, let the account to be created and configured automatically when you run the WSFC High Availability wizard.	Steps for prestaging an account for a clustered service or application in Failover Cluster Step-by-Step Guide: Configuring Accounts in Active Directory.

[Top]

[Top]

Listener DNS Name

Specifies the DNS host name of the availability group listener. The DNS name is a string must be unique in the domain and in NetBIOS. This name can contain only alphanumeric characters, dashes (-), and hyphens (_), in any order. DNS host names are case insensitive. The maximum length is 15 characters.

For more information, see Requirements for the DNS Name of an Availability Group Listener, earlier in this topic.

Port

The TPC port used by this listener.

Network Mode

Indicates the TCP protocol used by the listener, one of:

DHCP

The listener will us a dynamic IP address that is assigned by a server running the Dynamic Host Configuration Protocol (DHCP). DHCP is limited to a single subnet.

Important

We do not recommend DHCP in production environment. If there is a down time and the DHCP IP lease expires, extra time is required to register the new DHCP network IP address that is associated with the listener DNS name and impact the client connectivity. However, DHCP is good for setting up your development and testing environment to verify basic functions of availability groups and for integration with your applications.

Static IP

The listener will use one or more static IP addresses. Additional IP addresses are optional. To create an availability group listener across multiple subnets, for each subnet you must specify a static IP address in the listener configuration. Contact your network administrator to get these static IP addresses.

If you select Static IP a subnet grid appears below the Network Mode field. This grid displays information about each subnet that can be accessed by this availability group listener. This grid is empty until you add a static IP address by clicking Add.

The columns are as follows:

Subnet

Displays the identifier of each subnet that you add to the availability group listener.

IP Address

Displays the IP address of a given subnet. For a given subnet, the IP address is either an IPv4 address or an IPv6 address.

Add

Click to add to add a static IP address to a selected subnet or to another subnet for this listener. This opens the Add IP Address dialog box. For more information, see the Add IP Address Dialog Box (SQL Server Management Studio) help topic.

Remove

Click to remove the selected subnet from this listener.

OK

Click to create the specified availability group listener.

[Top]

When you use SQL Server Management Studio, Transact-SQL, or PowerShell to create an availability group listener, the Client Access Point is created in WSFC with the RegisterAllProvidersIP property set to 1 (true). The effect of this property value depends on the client connection string, as follows:

• Connection strings that set MultiSubnetFailover to true

  AlwaysOn Availability Groups sets the RegisterAllProvidersIP property to 1 in order to reduce re-connection time after a failover for clients whose client connection strings specify MultiSubnetFailover = yes (or true), as recommended. Note that to take advantage of the listener multi-subnet feature, your clients might require a data provider that supports the MultiSubnetFailover keyword. For information about driver support for multi-subnet failover, see "5.7.1 Client-Connectivity for AlwaysOn Availability Groups" in the SQL Server 2012 Release Notes.

  For information about multi-subnet clustering, see SQL Server Multi-Subnet Clustering (SQL Server).

  Tip
  When RegisterAllProvidersIP = 1, if you run the WSFC Validate a Configuration Wizard on the WSFC cluster, the wizard generates the following warning message: "The RegisterAllProviderIP property for network name 'Name:<network_name>' is set to 1 For the current cluster configuration this value should be set to 0." Please ignore this message.

• Connection strings that do not set MultiSubnetFailover to true

  When RegisterAllProvidersIP = 1, any clients whose connection strings do not use MultiSubnetFailover = yes (or true), will experience high latency connections. This occurs because these clients attempt connections to all IPs sequentially. In contrast, if RegisterAllProvidersIP is changed to 0, the active IP address is listed in the Client Access Point in the WSFC cluster, reducing latency for legacy clients.

  Therefore, if you have legacy clients that that need to connect to an availability group listener and cannot use the MultiSubnetFailover property, we recommend that you change RegisterAllProvidersIP to 0. The following PowerShell example demonstrates how to do this. Replace yourListenerName with the name of the listener that you are changing.

  Copy

  Import-Module FailoverClusters
  Get-ClusterResource yourListenerName|Set-ClusterParameter RegisterAllProvidersIP 0
  

  For information about available options and workarounds, see "5.7.1 Client-Connectivity for AlwaysOn Availability Groups" in the SQL Server 2012 Release Notes and Client Recovery Latency During Failover.

After you create an availability group listener:

• Ask your network administrator to reserve the listener's IP address for its exclusive use.

• Give the listener's DNS host name to application developers to use in connection strings when requesting client connections to this availability group.

• Encourage developers to update client connection strings to specify MultiSubnetFailover = yes (or true), if possible. For information about driver support for multi-subnet failover, see "5.7.1 Client-Connectivity for AlwaysOn Availability Groups" in the SQL Server 2012 Release Notes.

[Top]

After you create one listener through SQL Server, you can add an additional listener, as follows:

1. Create the listener using either of the following tools:

   • Using WSFC Failover Cluster Manager:

     1. Add a client access point and configure the IP address.

     2. Bring the listener online.

     3. Add a dependency to the WSFC availability group resource.

     For information about the dialog boxes and tabs of the Failover Cluster Manager, see User Interface: The Failover Cluster Manager Snap-In.

   • Using Windows PowerShell for failover clusters:

     1. Use Add-ClusterResource to create a network name and the IP address resources.

     2. Use Start-ClusterResource to start the network name resource.

     3. Use Add-ClusterResourceDependency to set the dependency between the network name and the existing SQL Server Availability Group resource.

     For information about using Windows PowerShell for failover clusters, see Overview of Server Manager Commands.

2. Start SQL Server listening on the new listener. After creating the additional listener, connect to the instance of SQL Server that hosts the primary replica of the availability group and use SQL Server Management Studio, Transact-SQL, or PowerShell to modify the listener port.

Important

When you create an availability group listener through the WSFC cluster (Failover Cluster Manager GUI), RegisterAllProvidersIP will be 0 (false) by default. When RegisterAllProvidersIP is 0, only the active IP address is registered. This will increase re-connection time after a failover. To avoid this, change RegisterAllProvidersIP to 1 for the listener, and use MultiSubnetFailover = yes (or true) in your application connection string. The following PowerShell example demonstrates how to change RegisterAllProvidersIP to 1 for the listener. Replace yourListenerName with the name of the listener that you are changing. Import-Module FailoverClusters Get-ClusterResource yourListenerName|Set-ClusterParameter RegisterAllProvidersIP 1

For more information, see How to create multiple listeners for same availability group (a SQL Server AlwaysOn team blog).