H3C Technologies H3C S10500 Series Switches - Manual (Page 93)

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The DNS client is made up of the resolver and cache. The user program and DNS client can run on the
same device or different devices, but the DNS server and the DNS client usually run on different devices.
Dynamic domain name resolution allows the DNS client to store latest mappings between domain names
and IP addresses in the dynamic domain name cache. The DNS client does not need to send a request
to the DNS server for a repeated query next time. The aged mappings are removed from the cache after
some time, and latest entries are required from the DNS server. The DNS server decides how long a
mapping is valid, and the DNS client gets the aging information from DNS messages.
DNS suffixes
The DNS client holds a list of suffixes which the user sets. The resolver can use the list to supply the missing
part of incomplete names.
For example, a user can configure com as the suffix for aabbcc.com. The user only needs to type aabbcc
to obtain the IP address of aabbcc.com because the resolver adds the suffix and delimiter before passing
the name to the DNS server.
• If there is no dot in the domain name (for example, aabbcc), the resolver considers this a host name
and adds a DNS suffix before the query. If no match is found after all the configured suffixes are
used respectively, the original domain name (for example, aabbcc) is used for the query.
• If there is a dot in the domain name (for example, www.aabbcc), the resolver directly uses this
domain name for the query. If the query fails, the resolver adds a DNS suffix for another query.
• If the dot is at the end of the domain name (for example, aabbcc.com.), the resolver considers it a
Fully Qualified Domain Name (FQDN) and returns the query result, successful or failed. The dot (.)
is considered a terminating symbol.
The device supports static and dynamic DNS client services.
NOTE:
If an alias is configured for a domain name on the DNS server, the device can resolve the alias into the IP
address of the host.
Configuring the IPv4 DNS client
Configuring static domain name resolution
Configuring static domain name resolution refers to specifying the mappings between host names and
IPv4 addresses. Static domain name resolution allows applications such as Telnet to contact hosts by
using host names instead of IPv4 addresses.
Follow these steps to configure static domain name resolution:
To do… Use the command… Remarks
Enter system view system-view ––
Configure a mapping between a host
name and an IPv4 address
ip host hostname ip-address
Required
Not configured by default.
NOTE:
•
The IPv4 address you last assign to the host name overwrites the previous one if there is any.
• You may create up to 50 static mappings between domain names and IPv4 addresses.