I hate to be that guy begging for help, but this is absolutley the first time I have worked on firewalling & routing at all so I guess it is what it is. Please forgive my excessive lack of knowledge on the subject. I have an ASA5505 that I am having a difficult time getting to do what I want.
If i turn DHCP server on in my ISP router and plug a single workstation into the ASA where the workstation recieves a DHCP address from the firewall (or any combination of static IP addresses within this range so long as the inside interface is not changed from the default 192.168.x.x) the out of the box config will work and the workstation can access the internet in this manner:
ISP router -> ASA -> workstation.
In this scenario the ISP router is performing the NAT from internal to public IP.
As soon as I start doing anything else to try to configure the device to fit into my internal IP scheme nothing works right. I am trying to reconfigure the "inside" interface to the IP addressing scheme I already have setup and set the outside interface to something between the ASA and the ISP router.A simple single switched internal network gaining internet access.
I could just reconfigure my DHCP server to make everything inside work with the cisco out of the box config or let the ASA do the DHCP for the network, but at this point I want to actually learn how to manipulate this device correctly.
I've found a basic config guide from Cisco and the network diagram here is pretty much what I want:
I have set the firewall up this way on a couple occasions with no success thus far.
Do I need to to setup the ISP firewall in a pass through mode and let the ASA do the NAT translation? Is there something else I am missing?
any help is appreciated.