For software I am developing, I need to have a list of external IP addresses that Google App Engine uses for urlFetch requests. Getting a complete list is proving difficult.
The accepted wisdom as detailed on SO is to use the output from...
dig -t txt _netblocks.google.com
...but unfortunately this list is incomplete. For example, my urlFetch requests currently emerge from unlisted addresses:
Is there any way to get an actively updated list of external IP addresses used by urlFetch?
The official advice is https://developers.google.com/appengine/kb/general#static-ip. Note that relying on Static IP addresses is bad, for all the reasons listed on that page.