Configure session persistence

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By default, Azure Load Balancer distributes network traffic equally among multiple VM instances. The load balancer uses a five-tuple (source IP, source port, destination IP, destination port, and protocol type) hash to map traffic to available servers. It provides stickiness only within a transport session.

Illustration of hash-based distribution with a load balancer and 3 virtual machines.

Session persistence specifies how traffic from a client should be handled. The default behavior (None) is that successive requests from a client may be handled by any virtual machine. You can change this behavior.

  • None (default) specifies any virtual machine can handle the request.
  • Client IP specifies that successive requests from the same client IP address will be handled by the same virtual machine.
  • Client IP and protocol specifies that successive requests from the same client IP address and protocol combination will be handled by the same virtual machine.

Note

Keeping session persistence information is important in applications that use a shopping cart. Can you think of any other applications?