[Edit, 7/7/16: Updating this post with the current range of IP addresses.]
Recently Authorize.Net migrated to a new data center to further enhance the performance and security of our platform. As part of the new platform changes, Relay Response and Silent Post data will now originate at these IP addresses:
If you have a firewall that blocks inbound Internet traffic and use Relay Response or Silent Post, please add these IP addresses to your whitelist.
@RichardH This is the IP address that was captured by our server during a silent post request: 18.104.22.168, after whitelisting this IP the silent post worked, but only whitelisting the two you've stated above did not help.
This is a legacy post, but I'll refresh it shortly with more current IP addresses.
As Authorize.Net expands out its data centers, IP addresses are subject to change, but we'll strive to keep information about IP addresses up to date.
@iamreb -- there's actually four IP addresses you should whitelist: The two listed previously; the one you found, and one other. Check the post for the full IP address range. Thanks.
We haven't changed these IP addresses since we posted them. We expect this list to remain stable for the foreseeable future. When we retire our legacy data centers, we'll drop two of the IP addresses, but that isn't going to happen for some time. The only additions were to support new data centers which we brought online, and we are using Network Address Translation, so even new servers should not change this list.
Again, this list should not change for some time, and when it does, it will be to retire IP addresses, not add new ones.