3Com Switch 8800 Family Firewall Module Configuration and Command Reference Guide

166 CHAPTER 10: ATTACK PREVENTION AND PACKET STATISTICS
Configuring a DNS
Server
For DNS domain name resolution, a domain name server address is required so
that the query request message can be sent to the correct server for resolution.
You can use the following commands to configure or remove the IP address of a
DNS server.
Perform the following configuration in system view.
By default, no DNS server is configured.
Configuring DNS Cache When resolving a name, a DNSC caches the result returned by the name server. In
this way, upon receiving a request for resolving the same name, the DNSC can
directly search for the name in the DNS cache, instead of sending a query request
to the name server again. This reduces network traffic.
Perform the following configuration in system view.
By default, no DNS cache entry is configured.
Displaying and
Debugging DNS Client
Configuration
After the above-mentioned configuration, you can display the DNS client
configuration by using the display command in any view, so as to verify the
configuration. You can debug DNS client configuration by using the debugging
command in user view.
Tabl e 193 Configure a DNS server
Operation Command
Configure a DNS server IP address dnsc server ip ip-address
Remove the DNS server IP address configured undo dns server { all | ip ip-address ]
Tabl e 194 Configure the DNS cache
Operation Command
Add a DNS cache entry
dnsc cache add domain domain-name type { a | mx } ip
ip-address ttl ttl
Remove a DNS cache entry
dnsc cache delete domain domain-name type { a | mx }
undo dnsc cache { all | domain domain-name type { a |
mx } }
Tabl e 195 Display and debug DNS client configuration
Operation Command
Display DNS client configuration display dnsc { server | cache }
Enable DNS client debugging debugging dnsc
Disable DNS client debugging undo debugging dnsc