API integrations with Authorize.net must be able to reach our fully qualified domain names to function properly, because we may reassign IP addresses without prior notification. You may need to whitelist the domains or associated IP addresses if you use a firewall.
If your integration also receive webhook notifications from Authorize.net, you might want to whitelist and verify that the calls are coming from our webhooks IP Addresses.
For API endpoints behind Akamai SureRoute, we are not able to provide IP addresses, due to the nature of Akamai address allocation. We recommend that merchants using Akamai API endpoints (http://secure2.authorize.net and http://api2.authorize.net) allow Internet traffic from any IP address. Fourth-generation firewalls should allow domain-level whitelisting.