DNS proxy
As shown in Figure 32, the DNS proxy performs the following operations:
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 32: DNS proxy application
A DNS proxy operates as follows:
A DNS client considers the DNS proxy as the DNS server, and sends a DNS request to the DNS proxy. The destination address of the request is the IP address of the DNS proxy.
The DNS proxy searches the local static domain name resolution table and dynamic domain name resolution cache after receiving the request. If the requested information is found, the DNS proxy returns a DNS reply to the client.
If the requested information is not found, the DNS proxy sends the request to the designated DNS server for domain name resolution.
After receiving a reply from the DNS server, the DNS proxy records the IP address-to-domain name mapping and forwards the reply to the DNS client.
If no DNS server is designated or no route is available to the designated DNS server, the DNS proxy does not forward DNS requests.