Book Image

Designing and Implementing Linux Firewalls and QoS using netfilter, iproute2, NAT and l7-filter

By : Lucian Gheorghe
Book Image

Designing and Implementing Linux Firewalls and QoS using netfilter, iproute2, NAT and l7-filter

By: Lucian Gheorghe

Overview of this book

Firewalls are used to protect your network from the outside world. Using a Linux firewall, you can do a lot more than just filtering packets. This book shows you how to implement Linux firewalls and Quality of Service using practical examples from very small to very large networks. After giving us a background of network security, the book moves on to explain the basic technologies we will work with, namely netfilter, iproute2, NAT and l7-filter. These form the crux of building Linux firewalls and QOS. The later part of the book covers 5 real-world networks for which we design the security policies, build the firewall, setup the script, and verify our installation. Providing only necessary theoretical background, the book takes a practical approach, presenting case studies and plenty of illustrative examples.
Table of Contents (14 chapters)
Designing and Implementing Linux Firewalls and QoS using netfilter, iproute2, NAT, and L7-filter
Credits
About the Author
About the Reviewer
Preface
Index

Summary


In this chapter, we saw that:

  • Layered models for networking communication allow interoperability, ease of use, and a faster growth of the Internet.

  • The TCP/IP model is the most popular model, but the OSI model is used as a reference in network communication. For example, TCP, which is at TCP/IP Layer 3, is referred to as a Layer 4 protocol.

  • TCP is a connection-oriented and reliable protocol that implements flow-control, while UDP is much simpler, and provides connectionless, unreliable delivery of packets.

  • IP classes A, B, C, D, and E were defined.

  • Subnetting is a process to divide an IP class into smaller pieces by borrowing bits from the host part of the IP address to the network part.

  • CIDR or IP supernetting is an IP addressing scheme that allows a more efficient management of IP addresses and aggregation for reducing the size of routing tables.

  • Providers exchange routing information using the Border Gateway Protocol, thus making the Internet work.