Can we have multiple listeners configured in multi-subnet always on?

Multi-Subnet SQL Server Always On Availability Groups. In the case of a multi-subnet, we need to use multiple IPs for the SQL listener. We need to configure one virtual IP for each subnet. Therefore, if we have a configuration for DC-DR Always on replicas, we can have one virtual IP for DC and one virtual IP for DR.

What is a multi-subnet?

When Multi-Subnet Failover is enabled, the driver simultaneously attempts to connect to all IP addresses associated with the Availability Group listener when the connection is broken or the listener IP address becomes unavailable. The first IP address to successfully respond to the request is used for the connection.

What is always on high availability in SQL Server?

SQL Server 2017 introduces two different architectures for availability groups. Always On availability groups provide high availability, disaster recovery, and read-scale balancing. These availability groups require a cluster manager. In Windows, failover clustering provides the cluster manager.

What is always on availability group listener?

An availability group listener is a virtual network name (VNN) that clients can connect to in order to access a database in a primary or secondary replica of an Always On availability group. A listener allows a client to connect to a replica without having to know the physical instance name of the SQL Server.

What is multi-subnet AlwaysOn availability group?

A SQL Server multi-subnet failover cluster is a configuration where each failover cluster node is connected to a different subnet or different set of subnets. These subnets can be in the same location or in geographically dispersed sites.

How do I add a listener to availability group?

Configuring the Listener

1. After creating the Availability Group, you can configure the listener from Availability Groups -> Group Name -> Add Listener.
2. You can configure the Network Mode as DHCP (Dynamic Host Configuration Protocol).
3. Additionally, you can script out the changes to a query window and see T-SQL script.

How do you create an availability group listener?

What is multi subnet failover?

A SQL Server multi-subnet failover cluster is a configuration where each failover cluster node is connected to a different subnet or different set of subnets. Therefore, a multi-subnet failover cluster provides a disaster recovery solution in addition to high availability.

How do I add a database to my availability group?

Right-click the primary replica and select Add Database. The “Add Database to Availability Group” wizard is displayed. In the wizard, click Select Databases. A list of databases is displayed.

Why is SQL Server always on on subnets?

Because Node1 and Node2 are on the same subnet, this configuration provides additional local high availability. SQL Server FCI SQLCLUST1 includes Node1 and Node2. Node1 is on Subnet1. Node2 is on Subnet1 and Subnet2. SQL Server Setup sees this configuration as a multi-subnet cluster and sets the IP address resource dependency to OR.

How to add subnets to SQL Server AlwaysOn availability group?

Because not all of the IP addresses returned by DNS will be online. Now click on the “Add…” button to assign IP addresses to listener “DBlistener”. We can see all three IPs from each subnet which are added for listener “DBlistener” in the below screenshot.

Why is SQL Server not considered a multi subnet cluster?

NOTE: This configuration is not considered as a multi-subnet failover cluster configuration because the clustered nodes are on the same set of subnets. In a multi-subnet failover cluster configuration, the IP addresses are not owned by all the nodes in the failover cluster, and may not be all online during SQL Server startup.

How to enable always on availability in SQL Server?

Right click on the SQL Server service and select properties. Select the “AlwaysOn High Availability” tab, and check the box to enable it. You will see the Windows cluster name which will be automatically fetched by this service in the “Windows failover cluster name” section.

Can we have multiple listeners configured in multi subnet always on?

Multi-Subnet SQL Server Always On Availability Groups. In the case of a multi-subnet, we need to use multiple IPs for the SQL listener. We need to configure one virtual IP for each subnet. Therefore, if we have a configuration for DC-DR Always on replicas, we can have one virtual IP for DC and one virtual IP for DR.

Can a database belong to multiple availability groups?

The cluster node can participate in multiple availability groups, with one replica from each group. Ask your database administrators how many cluster nodes are required for to support the availability replicas of the planned availability groups.

What is a high-availability group?

An availability group supports a replicated environment for a discrete set of user databases, known as availability databases. You can create an availability group for high availability (HA) or for read-scale. An HA availability group is a group of databases that fail over together.

Can a server have more than one availability group?

These IP addresses serve as ingress for the traffic. Because of this we can have multiple Availability Groups in the same Replica Server each one with his own Listener, to do this we need to follow the next steps:

What happens when you create an availability group Listener?

When you create a listener, it becomes a resource in a cluster with an associated virtual network name (VNN), virtual IP (VIP), and availability group dependency. A client uses DNS to resolve the VNN into multiple IP addresses and then tries to connect to each address, until a connection request succeeds or until the connection requests time out.

Can you use DHCP on an availability group Listener?

Using DHCP can cause connectivity delays during failover, and so it is not recommended for use in production environments. Availability groups that extend across multiple subnets, or use hybrid network configurations, must use a static IP address. When configuring an availability group listener, you must designate a port.

Can a cluster move all basic availability groups?

In almost all cases, the cluster will move all of the Basic Availability Groups together when a failover occurs. That’s the nature of failover clustering. However, there will be rare cases where one Basic Availability Group might end up in a different replica than the rest, for example, initiating a manual failover.