You cannot enter a network IP for gateway IP

Hi and Welcome to Sophos Community,

Gateway IP must be a specific IP address, it can never be technically correct to define a network address in this field.

Thanks

It is specific address. Please, see screenshots

HI  KrzysztofWitkowski , 

Could you check on Subnet Calculator and check if the interface address and Gateway is in the Range Host IP Range . Also could you Share your Subnet and Interface address. 

Thanks and Regards

Aditya Patel .

As Aditya Patel said,

the gateway IP address must in the WAN IP subnet range.

If you assign an out of range IP on gateway, it will show the alert to warn you.

You're right: gateway is not in the host's range. Thanks for confirmation.