A record (host name resolution), cname (alias resolution), and URL Forwarding (Domain Name forwarding)

What are a records (host name resolution), cname (alias resolution), and URL Forwarding (Domain Name forwarding )?

A record (host name resolution) is the most common domain name resolution, is to resolve a host name to an IP.

For example, www. ***. com-> ipv102.23.158, access www. ***. com requests will be resolved to ipv102.23.158 through DNS. (Note that this IP address is randomly written.) This is the most important thing in DNS resolution.

Cname (alias resolution) is the ing between the host name and the host name. It is used to resolve a host name to another host name.

For example, BBS. ***. com-> www. ***. com, access all BBS. * ** requests for domain names ending with 8.com will be resolved to www through DNS. ***. the IP address pointed to by COM;

URL Forwarding (Domain Name forwarding) is the ing between addresses. It directs a URL address to another URL address.

For example, http: // blog. ***. com to http: // www. ***. COM/blog. You only need to access http: // blog. ***. com to access http: // www. ***. COM/blog, which makes it easy for users to remember.

What is domain name resolution?

Domain name resolution is the process of converting the domain name to the IP address. An IP address is a digital address that identifies your site on the Internet. To make it easy to remember, use a domain name instead of an IP address to identify the site address. Domain name resolution is completed by the DNS server.

What is a record?

The A (Address) record is used to specify the IP address record corresponding to the Host Name (or domain name. You can direct the website server under this domain name to your web server. You can also set a second-level domain name for your domain name.

What is an MX record?

The mail route record. You can direct the mail server under the domain name to your own mail server, and then you can control all mailbox settings on your own. You only need to enter the IP address of your server online to transfer all emails under your domain name to your own email server.

What is a cname record?

That is, the alias record. This record allows you to map multiple names to the same computer. It is usually used on computers that provide both WWW and mail services. For example, there is a computer named "host.mydomain.com" (a record ). It provides WWW and mail services at the same time, in order to facilitate user access to the service. You can set two aliases (cname) for the computer: WWW and mail. The two aliases are www.mydomain.com and "mail.mydomain.com ". In fact, they all point to "host.mydomain.com ".

What is the TTL value?

The full name of TTL value is "time to live". Simply put, it indicates the cache time of DNS records on the DNS server. To understand the TTL value, take a look at the following example:

Assume that the IP address of the domain name myhost.abc.com (in fact, this is a DNS record, which usually indicates that there is a host named myhost in the abc.com domain) is 1.1.1.1, and its TTL is 10 minutes. This domain name or record is stored on a DNS server named dns.abc.com.

Now there is a user in the browser to type the address (also called URL): http://myhost.abc.com what will happen at this time?

the visitor's specified DNS server (or its ISP or Internet Service Provider) 8.8.8.8 tries to explain myhost.abc.com to him, of course, because the DNS server 8.8.8.8 does not contain the message "myhost.abc.com", it cannot be resolved immediately. However, after recursive queries by global DNS, the DNS server "dns.abc.com" is finally located, dns.abc.com: the DNS server sends the IP address 1.1.1.1 of myhost.abc.com to 8.8.8.8. However, 8.8.8.8.8.8 tells the user the result. 8.8.8.8 in order to accelerate the resolution of the myhost.abc.com record in the future, the 1.1.1.1 result will be retained for a period of time. This is the TTL time, during this period, if the user has another resolution request for the myhost.abc.com record, it will directly tell the user 1.1.1.1. When the TTL expires, the above process will be repeated.