Dns Proxy - HP A5120 EI Series Configuration Manual

Figure 33 shows the relationship between the user program, DNS client, and DNS server.
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. There is no 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 can be defined by users. The resolver can uses 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 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 switch supports static and dynamic DNS client services.
NOTE:
If an alias is configured for a domain name on the DNS server, the switch can resolve the alias into the
IP address of the host.

DNS proxy

Introduction to DNS proxy
A DNS proxy forwards DNS requests and replies between DNS clients and a DNS server.
As shown in
to the designated DNS server, and conveys the reply from the DNS server to the client.
The DNS proxy simplifies network management. When the DNS server address is changed, you can
change the configuration on only the DNS proxy instead of on each DNS client.
Figure 34, a DNS client sends a DNS request to the DNS proxy, which forwards the request
79