how long azure ilb keep the session afinity if i enabled 3 tulple hashing

Question

Hi ,

Does Azure ILB has any timeout or clear the session affinity when 3 tuple hashing enabled? or always session goes to the same VM when same client ip and protocol matches?

Scenario:

Azure ILB behind two vm's:

same client ip is sending TCP traffic , if first backend VM is taking traffic, If the connection closes subsequent goes to the same VM?

Is that flows goes to same vm forever until that vm goes down? or is the any session cache expiry time on Azure ILB?

Answer 1

Hi @JAYAKUMAR, PRABHUDOSS ,

Welcome to the Microsoft Q&A Platform. Thank you for reaching out & I hope you are doing well.
I understand that you would like to know how long Azure Load Balancer would maintain the session affinity.

Azure Load Balancer uses Hashing mechanisms to distribute traffic.
The Hashing Function(s) used will not change, so, this means, as long as none of the VMs go down, the traffic from same source and protocol should go to the same backend VM only.

In other words, there are no expiry for this hashing.

Kindly let me know if you have further questions on this.

Cheers,
Kapil

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