application recommendation

Hey guys,

I have a need for your candid opinion. I am searching for an enterprise
sized application (commercial or otherwise) that can accomplish diversified
network access from the inside. This is roughly the situation:

A diversified very large (multinational) enterprise, consisting of a
multitude of local networks. Each of the local networks provide direct
hard-wired local and Internet access with our equipment to our employees.

Our company has many third-party users. We would want to provide to the
latter (after a secure admission session) Internet access with their own
equipment through our (the same hard-wired) connection (and subsequently
with our firewall services and using our corporate endpoint security), but
no access to the internal/local networks.

Which application would accomplish this?
Appreciating your recommendations.

Best,
Jack

Jack Ryan
Network Architecture
National Railway System
nsosoc@gmail.com