Devices that dont show up in the ARP table



  • I have a pfSense machine at home with several ethernet ports, so ive decided to make a couple different subnets. The main system is on a 192.168.1.X. I built a computer for IP cameras and recording, assigned a static IP address to it and put it on the 192.168.3.X.

    Right now, I only have a few cameras on it, and can look up their IP address with the security software. But, is there a way to look them up in pfSense? The ARP table lists the LAN connection and the computer, but thats it.



  • @aramp1

    The arp cache will only show devices that have recently communicated with pfSense. They could be quite busy with another device on the local LAN but not show up in the pfSense arp cache.


  • Rebel Alliance Developer Netgate

    If you have a direct physical link to the 192.168.3.0/24 segment on pfSense, then you can always install the nmap package and have it do an ARP scan of that network, which will actively probe and list all the devices it sees.

    Otherwise, as @JKnott said the ARP table is passive. It only shows entries of devices that have talked to the firewall recently, not all known devices.


  • Rebel Alliance Global Moderator

    Are you running dhcp on this 192.168.3? If so and the IP camera's are dhcp then you can look up their IPs in the dhcp leases. If they are not dhcp then you should "know" their ips - so why would you need to look them up in some arp table or dhcp lease listing?



  • I don’t know their MAC addresses to add them, so I turned on dhcp to add them. They are listed in the dhcp leases. Thank you!