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Cisco RVS4000 Security Router with VPN Administrator Guide 9
Networking and Security Basics
This chapter describes networking and security basics. It includes these sections:
•An Introduction to LANs, page 9
•The Use of IP Addresses, page 10
•The Intrusion Prevention System (IPS), page11

An Introduction to LANs

A router is a network device that connects two networks together.
The router connects your local area network (LAN), or the group of PCs in your
home or office, to the Internet. The router processes and regulates the data that
travels between these two networks.
The router’s Network Address Translation (NAT) technology protects your network
of PCs so users on the Internet cannot “see” your PCs. This feature keeps your
LAN remains private. The router protects your network by inspecting the first
packet received through the Internet port before delivering it to the final
destination on one of the Ethernet ports. The router inspects Internet port services
like the web server, ftp server, or other Internet applications, and, if allowed, it will
forward the packet to the appropriate PC on the LAN side.