RFC 1713 (rfc1713) - Page 2 of 13
Tools for DNS debugging
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RFC 1713 Tools for DNS debugging November 1994 On the other hand, many inconsistencies arise from this distributed nature: many administrators make mistakes in the way they configure their domains and when they delegate authority to sub-domains; many of them don't even know how to do these things properly, letting problems last and propagate. Also, many problems occur due to bad implementations of both DNS clients and servers, especially very old ones, either by not following the standards or by being error prone, creating or allowing many of the above problems to happen. All these anomalies make DNS less efficient than it could be, causing trouble to network operations, thus affecting the overall Internet. This document tries to show how important it is to have DNS properly managed, including what is already in place to help administrators taking better care of their domains. 2. DNS debugging To help finding problems in DNS configurations and/or implementations there is a set of tools developed specifically for this purpose. There is probably a lot of people in charge of domain administration having no idea of these tools (and, worse, not aware of the anomalies that may exist in their configurations). What follows is a description of some of these programs, their scope, motivations and availability, and is hoped to serve as an introduction to the subject of DNS debugging, as well as a guide to those who are looking for something to help them finding out how healthy their domains and servers are. Some prior knowledge from the reader is assumed, both on DNS basics and some other tools (e.g., dig and nslookup), which are not analyzed in detail here; hopefully they are well-known enough from daily usage. 2.1. Host Host is a program used to retrieve DNS information from name servers. This information may be used simply to get simple things like address-to-name mapping, or some more advanced purposes, e.g., performing sanity checks on the data. It was created at Rutgers University, but then Eric Wassenaar from Nikhef did a major rewrite and still seems to be actively working on improving it. The program is available from ftp://ftp.nikhef.nl/pub/network/host_YYMMDD.tar.Z (YYMMDD is the date of the latest release). By default, host just maps host names to Internet addresses, querying the default servers or some specific one. It is possible, though, to get any kind of data (resource records) by specifying different query types and classes and asking for verbose or debugging output, from Romao
