IP Address Block of Appengine Servers?

I'm working with a third party webservice who requires that all calls to their service are made from whiteliste开发者_如何学God IP addresses. That is, I must give them IP addresses from which I will be making calls to their service.

Problem is I'm using Google Appengine. Is there any way to get a static IP address when making outgoing http requests from Appengine? Failing that - is there a block of IP addresses that all requests will come from? I could get the entire bloc whitelisted. If this exists, how likely is it to change?

I know I could setup a simple Amazon EC2 instance to use as a proxy (will ask another question for how to do this specifically) but just wanted to make sure there was no other way.

I had the same problem a couple of weeks ago connecting via Urlfetch from Google App Engine to the Stack Exchange API (The team has promptly fixed the problem whitelisting all the GAE IPs).

The range of IP addresses that urlfetch connections may come from, can be found by performing the following DNS lookup:

dig -t TXT _netblocks.google.com @ns1.google.com 

Last I checked this wasn't possible. You can get the current IP address dynamically, but it isn't predictable.

Please note: _netblocks.google.com is apparently not accurate. Currently I have noticed that GAE connects from addresses not listed when you dig _netblocks, for example from 8.35.201.166.

This range is not listed in _netblocks, _netblocks2 or _netblocks3.

Current dig output: ip4:216.239.32.0/19 ip4:64.233.160.0/19 ip4:66.249.80.0/20 ip4:72.14.192.0/18 ip4:209.85.128.0/17 ip4:66.102.0.0/20 ip4:74.125.0.0/16 ip4:64.18.0.0/20 ip4:207.126.144.0/20 ip4:173.194.0.0/16