How often can MS Azure App Services Outbound IP addresses change?
<p>I'm using Azure App Services that calls an external API that uses white-listing of IP addresses for defense-in-depth protection. </p>

<p>I'm aware I can find my Outbound IP addresses of my App Services under the WebApp -> Settings -> Properties -> Outbound IP addresses (showing a list of 4 comma separated IP addresses) which can be supplied to the external API whitelist. I understand Microsoft publishes a regularly updated list of Azure datacenter's IP addresses for outbound traffic that I can whitelist: <a href="https://www.microsoft.com/en-us/download/details.aspx?id=41653" rel="noreferrer">https://www.microsoft.com/en-us/download/details.aspx?id=41653</a></p>

<p>The issue is the external API can only handle a number of IP addresses and not the full list of Azure datacenter IP's. Would it be safe to just provide the 4 comma separated IP addresses? Is there clear Microsoft documentation on how often or when the IP address can dynamically change?  </p>

<p>I have tried to look for the answer and found two external sites that suggested it only changes when moving Azure regions [Ref 2] or if you scale up/down (but scale out/in is apparently fine) [Ref 1]. Is this correct information?</p>

<p>Is the Azure App Services Environment the only other viable alternative in my situation?</p>