Sorry for the long post...
I'm using a Cisco ASA 5510. So far I'm not using any sub interfaces. But now all of my physical interfaces are used.
I have a guest-wireless network that I use just for guest laptops. In the past I've used one of the physical interfaces on the ASA as the gateway for this network, with a route defined to the outside interface. But now I need to use this physical interface for something else so I need to change the way the ASA handles the guest traffic.
I was thinking about either:
1. defining a sub-interface on the inside interface, setting it to a lower security level, and configuring this sub-interface as the gateway for my guest network. Since the sub-interface will be a lower security level than the inside interface, traffic from the sub-interface won't be allowed into the inside interface.
2. NOT use a sub-interface, but create access lists on my internal routers so that guest traffic will only be allowed out to the internet. Then all guest traffic will pass through the inside interface of the ASA, along with all the other internal traffic.
Which one is the best or most secure way to do it? If I use the first option I don't think I would need to define access lists on my internal routers because the gateway for the guest network would be the sub-interface on the ASA.
Thanks so much for any input!