This article is about how to fix the error "Error: the subnet mask must be wider than 255.255.252.0" when configuring a WLAN interface on the Firewall.
When configuring the WLAN interface on the firewall the UI shows the error message as "Error: The Subnet Mask must be wider than 255.255.252.0."Â The error while configuring is because of the value specified on SonicPoint/SonicWave Limit on the Interface.
SonicPoint/SonicWave Limit specifies the maximum number of SonicPoints allowed on this interface. This value determines the highest subnet mask you can enter in the Subnet Mask field. Â
To overcome the error change the SonicPoint /SonicWave Limit to 128 when using the network 192.168.10.1 with a subnet mask of 255.255.255.0.Â

Maximum subnet mask sizes allowed shows the subnet mask limit for each SonicPoint/SonicWave Limit selection and the number of DHCP leases available on the interface if you enter the maximum allowed subnet mask.
Available Client IPs assumes 1 IP for the firewall gateway interface, in addition to the presence of the maximum number of SonicPoints allowed on this interface, each consuming an IP address.    Â
                       
NOTE: Please click on link for assistance on configuring the wireless tunnel interface :How to configure Wireless interface on firewall ?