[Daily] DNS iterative Query Process and dns query Process

[Daily] DNS iterative Query Process and dns query Process

DNS is an application layer protocol, and the port numbers are tcp/53 and udp/53.
DNS query process, such as accessing www.test.com
1. The client queries www.test.com
2. query the preferred DNS server, in Linux/etc/resolv. conf, in Windows
3. If no Authorization Record for the test.com domain exists in the preferred DNS server, send the request to the "." root domain DNS server.
4. "." The root domain is passed to the "com" domain, "com" domain is passed to the "test.com" domain, iterative Query
5. If a record exists in the "test.com" domain, the corresponding IP address is returned to the preferred DNS server.
6. The preferred DNS server of the client sends the IP address www.test.com to the client.
7. After the domain name is successfully resolved, the client sends the http request to the Web server.
8. The Web server responds to the client's access request and the client can access the target host.

 

Verification:
Dig + trace www.sopans.com