Cisco Firewall Overlapping Internal Network Issue

[vesiclife1]

I am trying to protect an internal network from another internal network on the same subnet with a cisco 5505 firewall. I don't know if it is possible with the conifguration my boss would like to implement but I have attached a jpeg photo of the layout. 

[vesiclife1]

Do I need a router to get traffic on the same subnet to anoter network on the same subnet through the firewall?

[Pablo]

Hi,

Yeah you need another device in between, it's not possible to configure 2 firewall interfaces on the same subnet unless you have multi-context mode which is not supported on the 5505.

Even if you get that router in between, you'll have to do full network source address translation on the ASA and the router in order to protect the overlapping network.

I know you mentioned the addressing can't be changed but it seems the best route you can take is to break that class C subnet into two /25 nets.

HTH

Pablo

[vesiclife1]

Yep. I am going to change the subnet on one network and assign others to the servers.