I am running a trial of Port Mapper and every time I run the scan against a switch, I only get IP addresses for machines within the subnet of the machine that is running the scan. I understand that this is expected behavior but (unless I am reading this incorrectly) according to the manual if I add the router then it will do the MAC to IP lookup using the ARP cache on the router.
We are using a Cisco 3750 as a Layer 3 switch (effectively doing the routing between VLANs) and I have added this as a device in Port Mapper but I am still not getting the IP addresses for any devices in other VLANs. I have run a scan and the MAC address is not being mapped to an IP address even though the ARP cache on the Layer 3 switch contains an entry for the MAC address in question. What am I doing wrong?
Assuming you have added the router's SNMP details, the software should pick up MAC to IP address mappings from its cache.
If you go to the device management and click Test Connection, does the app show information from both the switch and the router as shown below? That's just to make sure it's reachable and user credentials are valid: