Skip to main content
segmentation_fault
segmentation_fault
Explorer III
October 28, 2022
Solved

Every few months some users can't connect to our Wifi network ( running out of 255 ip addresses )?

  • October 28, 2022
  • 1 reply
  • 5693 views

I've inherited a fortigate 60E in a business location. The owners say every few months people can't connect to the wifi network. The business gets dozens of people a day who connect to the Wifi. So my suspicion is the Fortigate is hitting some limit of 255 192.168.1.X ip addresses? In the past I would tell them to reboot the Internet modem going into the fortigate. That would clear things up. But now looking to get to the bottom of this and solve it :)

 

Here's what I see in the settings below. Ignore the "Guest Wifi VLAN" as nobody uses that as it does not work. Folks connect to the regular Wifi network and get a 192.168.1.x address.

 

wifi.PNG

 

Best answer by gfleming

Sure, try one day for now and see how it goes. If you still have issues you can reduce it to 6 hours and so on...

1 reply

gfleming
Staff
gfleming
Staff
October 28, 2022

Most likely a DHCP lease time issue. Set the DHCP lease time to something really short like 30 minutes. Especially if this wi-fi network services visitors who come and go. That way DHCP leases won't be stuck and filling up the table preventing new leases for new visitors.

 

If it's a concurrent connection issue (i.e. you have >255 users at once on the network) you need to increase the subnet size.

    segmentation_fault
    segmentation_faultAuthor
    Explorer III
    November 1, 2022

    Thanks. Whereabouts in the web GUI for the fortigate 60e can I edit the DHCP lease settings? At most we will have 50 concurrent users so I guess no need to increase the subnet size. However we have staff who connect to the Wifi everyday. Will changing the lease to 30 minutes potentially adversely affect them?

    gfleming
    Staff
    gfleming
    Staff
    November 1, 2022

    Depends on which version of FOS you are on. Later versions you can access Lease Time setting in GUI. But you will for sure be able to do it via CLI: https://docs.fortinet.com/document/fortigate/6.4.10/administration-guide/783526/dhcp-servers-and-relays (look at section for configuring lease time).

     

    Shortening the lease time should not adversely affect clients. If 30 minutes improves things you can slowly increase to 1 hour, 2 hours etc to see what works best. 

      Terms & ConditionsAccessibility statement