1.1 Description

Filtering is functionality used to forward and discard certain types of frames. It is used to strengthen network security. You can use filters to limit access to the network by each user. For example, even if WWW is relayed between the inside network and the outside network, telnet and ftp can be discarded. It prevents unauthorized access from the external network and prevents unnecessary information from being leaked from the internal network to the external network. The following figure shows an example of network configuration that uses filters.

Figure 1-1: Example of network configuration using filters

<Structure of this section>

• 1.1.1 Filter Overview

• 1.1.2 Flow detection

• 1.1.3 Receive-side flow detection mode

• 1.1.4 Transmit-side flow detection mode

• 1.1.5 Flow detection conditions

• 1.1.6 Access list

• 1.1.7 Implicit discard

• 1.1.8 Notes on using filters