DNS parsing process

First, the host resolves the order of the domain name

1. Find the Cache

2. Find the Hosts file for this machine

3. Find the DNS server

Note: When configuring IP and hostname, remember to modify the/etc/hosts file, because some applications in the host communication between processes, the host name of the machine, if the host name does not resolve correctly to a normal IP address, then it will cause the process communication problems. second, the concept of interpretationDNS (domain Name System) 1, a distributed database that maps to each other as domain names and IP (Internet Protocol address) addresses on the Internet, enabling users to access the Internet more easily without remembering to be read directly by the machine        Number of IP strings.        2, through the host name, finally get the hostname corresponding IP address process is called Domain name resolution (or host name resolution).        3, the DNS protocol runs on the UDP protocol, using the port number 53. 4, in the entire Internet system, the conventional used to identify the network device address is IP, but we enter the DNS, because the domain name is more convenient for people to remember, or so many sites, how people can remember all the IP address. Q: How does the browser use the domain name to query the URL corresponding to the IP (corresponding server address)?　　A:1, browser cache: The browser caches DNS records at a certain frequency.　　2, the operating system cache: If the browser cache can not find the required DNS records, then go to the operating system to find.　　3. Route cache: The router also has a DNS cache.　　4. The ISP's DNS server: The ISP is the abbreviation for the Internet Service Provider (Provider), and the ISP has a dedicated DNS server to respond to DNS query requests. 5, root server: The ISP's DNS server is not found, it will make a request to the root server, recursive query (DNS server first asked the root name server. com name server IP address, and then asked. com domain name server, and so on).

Q: On the Internet to find the IP address of a website, in their own browser input, but why not connect?

A: Large high concurrent sites may have more than one IP address, depending on the network they will have a lot of IP to do cluster. Some are through DNS to achieve load balancing, and some with squid to achieve.

DNS parsing process