• A Network Switch Mapping Solution

How to interpret and correct the Duplicate Hostnames Detected Error Message

The duplicate hostnames detected error message appears when the IP/Hostname database table is populated by one or more IPv4 addresses sharing the same hostname. Depending on whether you are doing a manual mapping or a command line triggered mapping, the message will either appear in a dialog box or in your default web browser.

New in version 2.50: we recognize that many devices now have more than one IP address, such as VOIP devices, so we added a checkbox in Global Settings to disable this popup message. The message no longer shows by default.

If Global Settings/Use IP/Hostname Resolver Table is CHECKED:
the table is not being cleared for every switch mapping during this session. This reduces DNS queries by storing the IP/hostname pairs in a table for use during successive queries. If you are seeing the error, first try clearing the table by going to the left control panel/Database Maintenance, select IP-Hostname Resolver, press Erase Viewed Table, then Yes. Then flush your local DNS cache by going to Command Prompt and issuing the ipconfig /flushdns command. If you remap and the error message continues to appear, you have a DNS problem where two or more IPs are sharing the same hostname - specifically a PTR record problem.

If Global Settings/Use IP/Hostname Resolver Table is CHECKED AND you rarely exit the software AND the Erase IP/hostname Resolver Table on Exit is CHECKED: you need to clear the table by exiting once a day or more frequently. Or manually clear it by going to the left control panel/Database Maintenance, select IP-Hostname Resolver, press Erase Viewed Table, then Yes.

If Global Settings/Use IP/Hostname Resolver Table is CHECKED the Erase IP/hostname Resolver Table on Exit is UNCHECKED: check the box in Global Settings labeled Erase IP/hostname Resolver Table on Exit. We highly recommend leaving it checked.

If Global Settings/Use IP/Hostname Resolver Table is UNCHECKED: the table is being cleared EVERY time you map a switch meaning the IPs are resolved to hostnames EVERY time. This causes the most DNS traffic. If you see the Duplicate Hostname error message here, flush your local DNS cache by going to Command Prompt and issuing the ipconfig /flushdns command. If you remap and the error message continues to appear, you have a DNS problem where two or more IPs are sharing the same hostname - specifically a PTR record problem.

Summary: the state of those two checkboxes controls when the IP/hostname table is cleared. You can manually clear it by going to the left control panel/Database Maintenance, select IP-Hostname Resolver, press Erase Viewed Table, then Yes. You should also manually clear your operating system DNS cache by going to Command Prompt and issuing the ipconfig /flushdns command. If the manual clearing methods fail to stop the error message, you have a DNS problem where more than one PTR record has the same hostname.