Configuring and Managing MPE/iX Internet Services (August 2002)

Chapter 8
DNS BIND/iX
DNS BIND Troubleshooting Steps
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3. Detailed Problem Description: Historical information is very valuable... is this a new DNS BIND
installation, or has the site suddenly started to experience problems? No matter what the history, you will
need to find out and document the exact symptoms being experienced.
It Used to Work: Find out if the DNS Administrator is aware of any configuration or network topology
changes that could be tied to the recent DNS BIND problems. Make a note of anything they can suggest.
Generally, these problems are caused by an incorrect configuration change, or some change in network
topology, resulting in lost connectivity to systems required by the DNS environment (no route to a
required system, an internal or external nameserver is down, system name/IP address change, poor
configuration, and so forth.
New Configuration: In 99% of DNS BIND problems, the cause is poor configuration. Unfortunately,
DNS is not an easy service for the novice to configure. There are many pitfalls waiting to trip a user. In a
new configuration situation, you’ll find the following steps will probably be needed.
4. Topology Information: Obtain and document a detailed description of the DNS topology used in this
environment, Information on all the involved systems will be needed. It’s important to be able to picture
how all the systems connect to one another and the inter-dependencies any have with one another. If
possible, an ASCII diagram of the topology is very often worth the effort (labeling each node with its
system and DNS information, see Figure 8-1).
Figure 8-1 Labeling Nodes
5. Configuration Gathering: Once you have a good understanding of the history, symptoms, and topology,
it’s time start examining the DNS configuration at the site. Relying on assumptions does not work with
DNS BIND troubleshooting.
This information is needed from each system.
• From ALL Systems:
a. Review the following files:
/etc/resolve.conf
/etc/nsswitch.conf (If present)
results for all lan interfaces
b. Run the following commands:
nettool.net.sys “conf;summ;gui”
linkcontrol@,S
netcontrol <NIname>;STATUS for each appropriate NI
c. From Nameservers:
All the information detailed above in “From ALL Systems”
/etc/named.conf (Or the customers equivalent)
The system’s db files
server1.cup.hp.com
IP Addr: 15.1.1.1
Function: Primary Nameserver
server2.cup.hp.com
IP Addr: 15.1.1.2
Function: Secondary Nameserver
foo.cup.hp.com
IP Addr: 15.1.1.3
Function: DNS User