What's the meaning of idle timeout on the public IP configuration page?

Question

Who can tell me the exact behavior of after the timeout? I bind the public IP to a VM directly, why there's a gateway bring a "idle timeout" to me? I bind the IP directly, without any NAT or lload balancer.

Answer 1

The idle timeout setting on the public IP configuration page in Azure Application Gateway controls how long a TCP connection can remain idle before it's closed. If there's no activity on the connection for the specified duration, the connection is closed. This setting is used to optimize resource utilization and prevent resource exhaustion. Even if you bind the public IP to a VM directly, the idle timeout setting is still relevant because it's a property of the public IP resource.

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References:

• Frequently asked questions about Application Gateway - General

Answer 2

@iseki zeroThank you for reaching out.

I understand you wish to know what the Idle timeout is setting available for a Public IP in Azure and what is behavior after the Idle timeout maximum is exceeded.

In this case of Public IP address as documented here this setting provides an adjustable inbound originated flow idle timeout of 4-30 minutes, with a default of 4 minutes, and fixed outbound originated flow idle timeout of 4 minutes.

This idle timeout setting basically keeps a TCP or HTTP connection open without relying on clients to send keep-alive messages. If a period of inactivity is longer than the timeout value, there's no guarantee that the TCP or HTTP session is maintained between the client and your cloud service.

This setting is useful when your application requires long running TCP connections. To avoid losing the connection, configure the TCP keep-alive with an interval less than the idle timeout setting or increase the idle timeout value.

I understand you have not set-up any Gateway or load balancer, this setting is added as a default to Azure public IP to support the scenario described above.

Hope this helps! Please let me know if you have any additional questions. Thank you!

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Answer 3

@iseki zero
I too have come across this. I want to ask if there is a way to configure this default value of 4 mins to something else. I am creating a service resource on Kubernetes which requires idle time of more than 4 mins so can I configure it in my yaml? if so what annotation can be used for the same? I do not want to manually configure the idle time for the public ip from the portal.