Internal IP Address Changing on an Azure Container Instances

Question

Internal IP Address Changing on an Azure Container Instances

LIGEngelsen 75

One of my Azure Container Instances is acquiring a new internal IP address after being online for 24+ hours.

The Activity Logs show no sign of the container stopping. Why would the container acquire a different IP address?

This is really annoying because I have a DNS record that resolves to the "preferred" internal IP. If I stop and start the container, when the container comes back online it consistently reacquires the original/preferred IP address.

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Answer 1

Welcome to Microsoft Q&A,

@LIGEngelsen I hope you are doing well,

What you're seeing can occur with Azure Container Instances even when there is no corresponding stop/start operation in the Activity Log.

Microsoft documents that the IP address of a container group is typically retained during updates, but it is not guaranteed to remain the same. Azure-internal events can cause the container group to be redeployed to a different underlying host, which can result in a different private IP address.Therefore, the absence of a stop/start entry in the Activity Log does not necessarily mean the underlying ACI host remained unchanged.

More importantly, a private IP address should not be treated as a permanent identity for an ACI container group. Microsoft explicitly recommends using a DNS name label to mitigate this scenario.

Also note that Azure Container Instances currently do not provide a persistent static private IP that survives redeployment/recreation of the container group.

So the behavior is not necessarily evidence of an unexpected container restart; it can be the result of Azure moving/redeploying the container group internally.

Recommended approach: treat the ACI IP as ephemeral and use DNS/service discovery instead of relying on the IP as a permanent address.

Documentation:

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