Dns Proxy - HPE FlexNetwork 5130 EI Series Layer 3-Ip Services Configuration Manual

2. The DNS resolver looks up the local domain name cache for a match. If the resolver finds a
match, it sends the corresponding IP address back. If not, it sends a query to the DNS server.
3. The DNS server looks up the corresponding IP address of the domain name in its DNS
database. If no match is found, the server sends a query to other DNS servers. This process
continues until a result, whether successful or not, is returned.
4. After receiving a response from the DNS server, the DNS client returns the resolution result to
the user program.
Caching
Dynamic domain name resolution allows the DNS client to store latest DNS entries in the DNS cache.
The DNS client does not need to send a request to the DNS server for a repeated query within the
aging time. To make sure the entries from the DNS server are up to date, a DNS entry is removed
when its aging timer expires. The DNS server determines how long a mapping is valid, and the DNS
client obtains the aging information from DNS responses.
DNS suffixes
You can configure a domain name suffix list so that the resolver can use the list to supply the missing
part of an incomplete name.
For example, you can configure com as the suffix for aabbcc.com. The user only needs to enter
aabbcc to obtain the IP address of aabbcc.com. The resolver adds the suffix and delimiter before
passing the name to the DNS server.
The name resolver handles the queries based on the domain names that the user enters:
•
If the user enters a domain name without a dot (.) (for example, aabbcc), the resolver considers
the domain name to be a host name. It adds a DNS suffix to the host name before performing
the query operation. If no match is found for any host name and suffix combination, the resolver
uses the user-entered domain name (for example, aabbcc) for the IP address query.
•
If the user enters a domain name with a dot (.) among the letters (for example, www.aabbcc),
the resolver directly uses this domain name for the query operation. If the query fails, the
resolver adds a DNS suffix for another query operation.
•
If the user enters a domain name with a dot (.) at the end (for example, aabbcc.com.), the
resolver considers the domain name an FQDN and returns the successful or failed query result.
The dot at the end of the domain name is considered a terminating symbol.

DNS proxy

The DNS proxy performs the following functions:
•
Forwards the request from the DNS client to the designated DNS server.
•
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 only on the DNS proxy instead of on each DNS client.
Figure 35 shows the typical DNS proxy application.
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