Introduction

What is high availability? In the strictest sense of the word, high availability (HA) means any system designed to ensure a particular (or estimated particular) operational uptime in a year. Therefore, a continuously available database server would have practically no down time in any given year.

HA has essentially come to mean redundant. System s can be designed with more reliable components, (all of which have to possess the desired Mean Time Before Failure [MTBF]) to achieve a projected 5 minutes of downtime in a given year). SonicWALL is the answer: two synchronized firewalls securing the same ingress and egress points, thus providing a redundant data path in the event that one becomes inoperable.

This chapter provides a look at the various features of SonicWALL firewalls that provide for HA. We begin with a cursory discussion of the justification for a HA network implementation. Having a rudimentary feel for the various aspects of this topic is a great help when required to justify potentially expensive, and redundant purchases to upper management. However, a truly in-depth discussion of such a broad topic is beyond the scope of this book.

After this, we examine how HA is achieved with specifically with SonicWALL firewalls. Configuration examples are provided that can be used as a baseline to architect HA solutions in your own network.

Towards the end of the chapter, we touch on some advanced configurations. Also, some potential pitfalls are considered and recommendations given on how to best mitigate them.

The Need for...