1. Introduction

A number of problems in DNS operations today are attributable to poor choices of secondary servers for DNS zones. The geographic placement as well as the diversity of network connectivity exhibited by the set of DNS servers for a zone can increase the reliability of that zone as well as improve overall network performance and access characteristics. Other considerations in server choice can unexpectedly lower reliability or impose extra demands on the network.

This document discusses many of the issues that should be considered when selecting secondary servers for a zone. It offers guidance in how to best choose servers to serve a given zone.