Sending inbound Web Service requests to ServiceNow using IP address instead of HostName.
Instance pairs ( Production/Sub-Production) hosted on the same data center may resolve to the same IP .
It is always recommended to send inbound web service call using the HostName of the ServiceNow instance
To send using IP address add 'Host' header in the inbound Web Service request .
For example use below header in the REST call to route to the right server