So, I had to set the att gateway to IP Passthrough mode. In this mode, the Cisco router receives the external WAN IP address directly passed through from the att gateway.
With that enabled, I also set the Cisco router to DHCP and removed the default gateway settings from the switch and turned off DHCP at the switch. Now I have internet.
I then added the router address (192.168.1.1) as the default gateway in the IPv4 settings by adding a static route with the following:
Destination IP Prefix 0.0.0.0
Prefix length 0
Next Hop Router 192.168.1.1
Metric 4 (default)
Still have internet.
Then I disabled DHCP on the Cisco router and gave my Ethernet connection a static IP of 192.168.1.5
Default gateway 192.168.1.1
Still have internet.
Next, on the switch:
enabled DHCP
Created a network pool from 192.168.1.2 to 192.168.1.253 (I intentionally excluded .1 and .254 as they are used by the router and switch)
Subnet mask 255.255.255.0
Default router IP address 192.168.1.254
Set my network card back to DHCP and renewed my ipconfig to get an IP address from the switch (default gateway listed is 192.168.1.254).
Lost internet
Something about my DHCP setup on the switch is killing the internet connection.
I went back into the IP address pool and set the Domain Name Server IP Address to the router address 192.168.1.1
I renewed my IP address on the network card just to refresh things and now the internet works????