What is multi-subnet cluster?
A SQL Server 2014 multi-subnet failover clustered instance is a configuration where each node of the cluster is connected to a different network subnet or subnets. These network subnets can be in the same location or in a remote site commonly used for disaster recovery.
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 does availability Group Listener work?
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 are the steps in multi-subnet availability group?
There are five steps outlined here: Change the RegisterAllProvidersIP parameter. Reduce the HostRecordTTL. The docs recommend 300 seconds (5 minutes), but you’ll need to determine the right value for your environment. Take the listener offline. Bring the listener back online.
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.
How to create availability group in SQL Server?
First we’ll need to enable the Availability Group feature on each SQL Server instance. On SQLCLU1, open the SQL Server Configuration Manger. Right click on the SQL Server service and select properties. Select the “AlwaysOn High Availability” tab, and check the box to enable it.
What do you need to know about multi subnet AGS?
This type of zone-redundant high availability is great for uptime, but does introduce one wrinkle for connectivity. With a default configuration, multi-subnet AGs require that the clients connecting to them include MultiSubnetFailover=true as a connection string attribute.