I am working on a scenario where i am using /21 mask with class C address. Now as i am running out of ip addresses i am thinking to increase my block size to /20 or /19. Right now with /21 mask no subnets have been configured except default vlan. There is an application firewall at the edge of network and has multiple internet connections and is doing all the NAT stuff and is configured with another class C address of 192.168.10.1 acting as a gateway for whole block of /21. what i want to do now is to increase the block size to /19 or /20 and configure subnets on my core switch so that i can make departmental vlans. My question here is with departmental vlans configured i have to change the gateway of to specific vlan ip so in this case how my application firewall which is acting as a gateway right now will function as i want users to restrict and follow policy on firewall. should i add this gateway ip 192.168.10.1 in proxy setting so that users are restricted accordingly ?? or there is something else i have to do in order to make this network work ?
