Networks, Routing, and Firewall Basics B-1
Appendix B
Networks, Routing, and Firewall Basics
This appendix provides an overview of IP networks, routing, and firewalls.
Related Publications
As you read this document, you may be directed to various RFC documents for further
information. An RFC is a Request For Comment (RFC) published by the Internet Engineering
Task Force (IETF), an open organization that defines the architecture and operation of the Internet.
The RFC documents outline and define the standard protocols and procedures for the Internet. The
documents are listed on the World Wide Web at www.ietf.org and are mirrored and indexed at
many other sites worldwide.
Basic Router Concepts
Large amounts of bandwidth can be provided easily and relatively inexpensively in a local area
network (LAN). However, providing high bandwidth between a local network and the Internet can
be very expensive. Because of this expense, Internet access is usually provided by a slower-speed
wide-area network
(WAN) link such as a cable or DSL modem. In order to make the best use of the
slower WAN link, a mechanism must be in place for selecting and transmitting only the data traffic
meant for the Internet. The function of selecting and forwarding this data is performed by a router.
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