Alias Interface

Hi Idris Sanni,

Thank you for reaching out to Sophos Community.

Sophos Firewall doesn't allow to create DHCP server on an alias interface.

If you have a manageable switch, then you can segregate your network into different VLANs. Later add the VLAN interface on Sophos Firewall and configure the DHCP server with that VLAN interface.

Add a VLAN interface

OR

If the IP pool is full then you can change the subnet mask of the current LAN interface to have multiple host addresses.

I want it on the firewall since it acts as the DHCP server.

However, i did not even thought of changing the mask from 24 to like 23 to accommodate additional IP.

if I change the mask, devices will not be able to communicate on the network

They will refresh next power on. Not only that, your existing ip range will be in the /23 so the users will be fine and your firewall rules will be updated.

What do you mean by "they will refresh on power on"?

Also I saw somewhere that leaving the mask of the subnet used up as /24, configure another vlan on the interface then making the switchport connected to the XG a trunk port can also resolve.

To get an updated subnet mask, you'll either need to renew the IP address configuration or need to reboot the end machine once.

As I suggested earlier you can configure VLAN on the manageable switch to distribute internal networks and then configure VLAN interface and DHCP server accordingly on the Sophos Firewall.

My fear is this, all my ubiquiti access points are connected to the switch, if I configure VLAN on that switch and assign ports to each of the VLANs created, there might not be communication between end devices.