This section gives examples of DNS configuration using
Microsoft DNS Server and BIND 8 & 9.
These examples show how to set up an SRV record to handle
H.323 URIs of the form user@example.com. These are handled
by the system with the fully qualified domain name of vcs.
example.com which is listening on port 1719, the default
registration port.

It is assumed that both A and AAAA records already exist
for vcs.example.com. If not, you will need to add one.

Verifying the SRV record

There are a range of tools available to investigate DNS records.
One commonly found on Microsoft Windows and UNIX platforms
is

nslookup. Use this to verify that everything is working as

expected.
For example:

•

nslookup -querytype=srv _ h323ls. _ udp.

example.com

and check the output.

Using Microsoft DNS Server you can add the SRV record using either the command line or the MMC snap-in.
To use the command line, on the DNS server open a command window and enter:

•

dnscmd . /RecordAdd domain service _ name SRV Priority Weight Port Target

where:

domain

is the domain into which you wish to insert the record

service _ name

is the name of the service you’re adding

Priority

is the priority as defined by

RFC 2782 [3]

Weight

is the weight as defined by

RFC 2782 [3]

Port

is the port on which the system hosting the domain is listening

Target

is the FQDN of the system hosting the domain

For example:

•

dnscmd . /RecordAdd example.com _ h323ls. _ udp SRV 1 0 1719 vcs.example.com

BIND is a commonly used DNS server on UNIX and Linux systems. Configuration is based around two sets of text files:

named.conf

which describes which zones are represented by the server, and a selection of zone files which describe the detail of each zone.
BIND is sometimes run chrooted for increased security. This gives the program a new root directory, which means that the
configuration files may not appear where you expect them to be. To see if this is the case on your system, run

•

ps aux | grep named

This will give the command line that named (the BIND server) was invoked with. If there is a

-t option, then the path following that is

the new root directory and your files will be located relative to that root.
In

/etc/named.conf look for a directory entry within the options section. This will give the directory in which the zone files are

stored, possibly relative to a new root directory. In the appropriate zone section, a file entry will give the name of the file containing the
zone details.

Overview

Microsoft DNS server

BIND 8 & 9

For more details of how to configure BIND servers and the DNS system in general see the publication

DNS and BIND [6]