D-Link DFL-210 - NetDefend - Security Appliance, User Manual

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3.9. DNS
Overview
A DNS server can resolve a Fully Qualified Domain Name (FQDN) into the corresponding numeric
IP address. FQDNs are unambiguous textual domain names which specify a node's unique position
in the Internet's DNS tree hierarchy. FQDN resolution allows the actual physical IP address to
change while the FQDN can stay the same.
A Uniform Resource Locator (URL) differs from an FQDN in that the URL includes the access
protocol along with the FQDN. For example the protocol might be specified http//: for world wide
web pages.
FQDNs are used in many aspects of a NetDefendOS configuration where IP addresses are unknown
or where it makes more sense to make use of DNS resolution instead of using static IP addresses.
DNS with NetDefendOS
To accomplish DNS resolution, NetDefendOS has a built-in DNS client that can be configured to
make use of up to three DNS servers. The are called the Primary Server, the Secondary Server and
the Tertiary Server. For DNS to function at least the primary must be defined. It is recommended to
have at least a primary and secondary defined so that there is a backup should the primary be
unavailable.
Features Requiring DNS Resolution
Having at least one DNS server defined is vital for functioning of the following modules in
NetDefendOS:
• Automatic time synchronization.
• Access to an external certificate authority server for CA signed certificates.
• UTM features that require access to external servers such as anti-virus and IDP.
Example 3.29. Configuring DNS Servers
In this example, the DNS client is configured to use one primary and one secondary DNS server, having IP
addresses 10.0.0.1 and 10.0.0.2 respectively.
CLI
gw-world:/> set DNS DNSServer1=10.0.0.1 DNSServer2=10.0.0.2
Web Interface
1. Go to System > DNS
2. Enter the following:
• Primary Server: 10.0.0.1
• Secondary Server: 10.0.0.2
3. Click OK
3.9. DNS Chapter 3. Fundamentals
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