Chapter 3 Configuring the Device
OPERATIONAL MODES
The NetScreen-5000 Series supports two operational modes: Transparent and Route. The default mode is Route.
Transparent Mode
In Transparent mode, a NetScreen-5000 Series systems operates as a Layer-2 bridge. Because the device cannot translate packet IP addresses, it cannot perform Network Address Translation (NAT). Consequently, for the device to access the Internet, any IP address in your trusted (local) networks must be routable and accessible from untrusted (external) networks.
In Transparent mode, the IP addresses for the Layer-2 Trust and Untrust zones are 0.0.0.0, thus making the NetScreen-5000 Series system invisible to the network. However, the device can still perform firewall, VPN, and traffic management according to configured security policies.
Route Mode
In Route mode, a NetScreen-5000 Series system operates at Layer 3. Because you can configure each interface using an IP address and subnet mask, you can configure individual interfaces to perform NAT.
•When the interface performs NAT services, the NetScreen-5000 Series system translates the source IP address of each outgoing packet into the IP address of the untrusted interface. It also replaces the source port number with a randomly-generated value.
•When the interface does not perform NAT services, the source IP address and port number in each packet header remain unchanged. Therefore, to reach the Internet your local hosts must have routable IP addresses.
For more information on NAT, see the NetScreen Concepts & Examples ScreenOS Reference Guide.
