We are trying to setup SQL server alwayson for an application, but as per the documentation we need the ILB to map the listener. Just want to understand why do i need the ILB in the VNet if there is no public access required/ every resource is available in the local network?

Thanks, Abhisek

1 Answer 1


Internal Load Balancer (ILB) requires Internal VIP as they are Layer 4 (TCP) load balancer where as external Load Balancer requires Public IP's as they function at layer 7 (DNS).

When we put the Azure Resources in Availability Set, for sure you wish to apply rules on how incoming request will be distributed inside the Availability Group/Set so that if any resources is offline for some region such as maintenance, still user's or application request will be entertained by your SQL Server. Its the part of Business Continuity solution with higher SLA rate however their could be a performance impact. Moreover, you can troubleshoot the issues and bring back your resource online and get same performance as expected. This will be possible with the help of Internal Load Balancer which will be listening/monitoring your SQL Instance health.

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