One possible reason could be that the switch does not return the MAC Addresses. Ensure that the switch is configured to return the values from the dot1dTpFdbTable of the Bridge MIB implemented in the switch. If you are not sure about this configuration, check with the Switch vendor. For example, in Extreme Summit switches, the command to enable this is: Enable snmp dot1dTpFdbTable
If problem persists, contact with the Support File.
The possible reasons could be:
One possible reason could be that the device connected to that port is a Switch/Hub. In that case, the Switch Port Managemenet tool will show the devices that are connected to that Switch/Hub.
This means that scanning of some of the switches imported from a csv file have failed. Click the link to view the details of the switches with its error details. Fix the errors by modifying the switch inputs and save. This will re-scan the switches to get the mapping details.
Routers specified in the Switch Port Mapper tool are used to resolve the IP Addresses of the connected devices. You can add all your routers in the Admin --> Add Router and schedule scanning. This will collect the MAC-IP data and updates the database. This data will be used by the Switch Port Mapper tool to resolve the IP Addresses of the connected devices.
One possible reason could be that we could not get the matching ports for all the ports of the switch from the Bridge MIB. The MAC Address of the devices connected to the switch port can only be resolved, if a matching port is found in the Bridge MIB. Selecting the "Show all the Interfaces" option from Switch Port Mapper settings will list all the ports of the switch, but the MAC Address will be resolved only for the ports that have an matching entry in the Bridge MIB.
One possibility that the MAC Address is not returned from the Bridge MIB could be because of the Switch Aging Time. Switches learns the MAC Addresses of the devices based on the data flowing through it. If there is not data flowing from a particular device, it will lose the data. This could be the reason for the MAC Address not being shown for a port that is UP. You can enhance the MAC resolution by using the SNMP Sweep option available in OpUtils.