The fee platform sends a callback with the fee outcome to the web service. The reply with the request processing outcomes is sent to the merchant’s internet service. IP address ranges, or netblocks, are groups of related IP addresses. They are normally represented as a base IP address, followed by a slash, and then a netmask which represents what number of IP addresses are contained inside the netblock. This format is called CIDR. You’ll also sometimes see netblocks given as a start ip tackle, and an end ip handle, or an ip handle range.