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Introduction 305
SmartWare Software Configuration Guide 28 • DNS configuration
Introduction
The domain name system (DNS) enables users to contact a remote host by using easily remembered text labels
(www.patton.com, for example) instead of having to use the host’s numeric address (209.45.110.15, for exam-
ple). When DNS names are entered as part of configuration commands or CLI exec mode commands in appli-
cations like Ping, Traceroute, or Tftp, the SmartNode uses a DNS resolver component to convert the DNS
names into the numeric address.
The SmartNode can be configured as a caching DNS relay server to speed data transfers, acting as the DNS
server for a private network. In this configuration, hosts in the network send their DNS queries to the Smart-
Node, which checks to see if the DNS name is in its DNS resolver cache. If it finds the name in cache, the
SmartNode uses the cached data to resolve the DNS name into a numeric IP address. If the name is not in
cache, the query is forwarded on to a DNS server. When the SmartNode receives the answer from the server, it
adds the name to the cache, and forwards it on to the host that originated the query. This process enables the
SmartNode to provide answers more quickly to often-queried DNS names, reducing the number of DNS que-
ries that must be sent across the access link.
DNS configuration task list
The following sections describe how to configure the DNS component:
• Enabling the DNS resolver
• Enabling the DNS relay
Enabling the DNS resolver
To enable the SmartNode DNS resolver, you must configure it with the address of one or more DNS servers
that will be used to resolve DNS name queries. If multiple DNS servers are configured, the SmartNode will
query each server in turn until a response is received. DNS servers are configured as follows:
Mode: Configure
Example: Configuring DNS servers
The following example shows how to add DNS servers to the SmartNode DNS resolver and increase the size of
the DNS cache to 100 entries.
node>enable
node#configure
node(cfg)#dns-client server 62.2.32.5
node(cfg)#dns-client server 62.2.100.45
node(cfg)#dns-client cache 100
Step Command Purpose
1 node(cfg)#dns domain-name server
server-ip-address
Add an IP address of a DNS server to be used
resolving DNS names
2 Repeat step 1 for each additional DNS server
you want to add
2 node(cfg)#dns-client cache number-of-entries Optional. Defines the maximum number of DNS
answers stored within the cache (default is 30)