Will the NAT ip changed on the Azure public peering
I have just enabled public peering on my ExpressRoute and have a question about the source NAT. I have been able to determine that the source IP address from which our connections appear to originate is 188.8.131.52, when connecting to Azure public services via the ExpressRoute. This address is not assigned to us by our ISP or ExpressRoute provider (in fact they can't explain where it comes from), so I assume it is assigned by MS? I opened a case about this ages ago (case 116100614763629) and the response seemed to confirm that the connection does indeed get double-NAT'd by MS.
My main concern is that we have no control over this address and that it therefore could change. This would be very bad for us as if it changes it could break some of our business critical services. For example, we have an external partner that host their FTP server in Azure and have whitelisted our on-premises public IP address. After determining that our Azure public peering address is 184.108.40.206, they have whitelisted this address and everything is working again, but if it changes for some reason, we won't be able to connect to them any more. Is it possible or likely that it will change without notice? Would we be notified in some way if it was to change? Thanks and regards, Matt.
Test Example commented
We had the same NAT in this arrangement for about 6 months and it just changed randomly with no warning. How do we know when this will happen again?