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3.3. Interfaces
3.3.1. Overview
An Interface is an important logical building block in NetDefendOS. All network traffic that transits
through, originates from or is terminated in the NetDefend Firewall, does so through one or more
interfaces.
Source and Destination Interfaces
An interface can be viewed as a doorway through which network traffic passes to or from
NetDefendOS. A NetDefendOS interface has one of two functions:
• The Source Interface
When traffic arrives through an interface, that interface is referred to in NetDefendOS as the
source interface (also sometimes known as the receiving or incoming interface).
• The Destination Interface
When traffic leaves after being checked against NetDefendOS's security policies, the interface
used to send the traffic is referred to in NetDefendOS as the destination interface (also
sometimes known as the sending interface).
All traffic passing through NetDefendOS has both a source and destination interface. As explained
in more depth later, the special logical interface core is used when NetDefendOS itself is the source
or destination for traffic.
Interface Types
NetDefendOS supports a number of interface types, which can be divided into the following four
major groups:
• Ethernet Interfaces
Each Ethernet interface represents a physical Ethernet port on a NetDefendOS-based product.
All network traffic that originates from or enters a NetDefend Firewall will pass through one of
the physical interfaces.
NetDefendOS currently supports Ethernet as the only physical interface type. For more
information about Ethernet interfaces, see Section 3.3.2, “Ethernet Interfaces”.
• Sub-interfaces
Some interfaces require a binding to an underlying physical interface in order to transfer data.
This group of interfaces is called Physical Sub-Interfaces.
NetDefendOS has support for two types of sub-interfaces:
• Virtual LAN (VLAN) interfaces as specified by IEEE 802.1Q. When routing IP packets over
a Virtual LAN interface, they will be encapsulated in VLAN-tagged Ethernet frames. For
more information about Virtual LAN interfaces, please see Section 3.3.3, “VLAN”.
• PPPoE (PPP-over-Ethernet) interfaces for connections to PPPoE servers. More information
about this topic can be found in Section 3.3.4, “PPPoE”.
• Tunnel Interfaces
3.3. Interfaces Chapter 3. Fundamentals
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