@OP
You could place a router/firewall between the AT&T router and the 24-port switch. This new "main" router would handle DNS/DHCP/etc for your network and in turn get it's WAN IP address from the AT&T router in front of it. The new router could just be an old PC in a 1U running pfSense, OPNSense, IPFire or just a plain command-line only Linux install with iptables. make sure it has at least two Ethernet ports or you'll have to deploy a VLAN-supporting switch and implement "router on a stick".
As a reference, I have a Pentium G5400 in a 1U running Proxmox VE with three pfSense instances and one Linux router instance as guests - clearly overkill for a 76Mb/18Mb VDSL connection, but it's a sandpit I can play in.
You could place a router/firewall between the AT&T router and the 24-port switch. This new "main" router would handle DNS/DHCP/etc for your network and in turn get it's WAN IP address from the AT&T router in front of it. The new router could just be an old PC in a 1U running pfSense, OPNSense, IPFire or just a plain command-line only Linux install with iptables. make sure it has at least two Ethernet ports or you'll have to deploy a VLAN-supporting switch and implement "router on a stick".
As a reference, I have a Pentium G5400 in a 1U running Proxmox VE with three pfSense instances and one Linux router instance as guests - clearly overkill for a 76Mb/18Mb VDSL connection, but it's a sandpit I can play in.
