Troubleshooting Offline DHCP Leases

The Status > DHCP Leases page only reports systems as “online” if the MAC address for a given system appears in the pfSense firewall’s ARP table. This can be verified by checking Diagnostics > ARP Table. Systems that have not communicated with or via the firewall in the past few minutes will appear as offline.

To check a system, try to ping it from Diagnostics > Ping. Even if the system does not respond to ping, that action will cause the system to appear in the ARP table if it is on the network, and would thus show online in the DHCP Leases list.

The arping package may also be of interest. It is available under System > Packages. The nmap package can also be used to perform an ARP-based subnet scan to locate online hosts even if they don’t respond to ICMP.