First of all, because the FW will also use IP to talk to other devices, so it is require to enable IP in router & FW. Unless you enable bridging at router and FW talk to the remote via the bridged router port, but it is not recommended.
For your situation, do you mean the FW & router will also require to use public IP ? If yes, thre are three ways to do it :
1) Enable NAT at the router and use private address between FW & router.
2) Borrow one /30 subnet from the /23 address, but will waste some IP.
3) Enable "IP Unnumber" at the LAN port at router which is connecting to the FW, and the FW and router's WAN use the same subnet (/23). FW will looks like to talk to the router's WAN port directly.
I recommend option 3 due to no IP wasted and simplier to configure the router.
We are pleased to announce availability of Beta software for 16.6.3. 16.6.3 will be the second rebuild on the 16.6 release train targeted towards Catalyst 9500/9400/9300/3850/3650 switching platforms. We are looking for early feedback from custome...