What is the role of the second-level domain name? How to resolve the second-level domain name
DomainCn
If you don't know what a second-level domain name is, or what it does, then this is the right place to come. By the way, I'll tell you how to resolve a second-level domain name. It's all useful information, so I suggest you save it.
Some time ago, I sent a URL to a friend: world.taobao.com, and wanted to recommend her to buy some daily necessities. After opening it, she asked a question: "Is this the URL of XX company?" Why is there "world" in front? It can't be fake! I laughed. It turns out that many people still don't know what a second-level domain name is. I decided to popularize it here.
1. What is a second-level domain name
There is endless debate about second-level domain name websites, and there is no unified conclusion, especially when the first, second, third and fourth levels are all laid out, it is even more confusing. In fact, there are many ways to display the skills, 1. Count the number of (.) from the back to the front, which is the level of the domain name, such as https://aa.xxx.com, with 2 dots, it is the second-level domain name. The first-level .com of the domain name is the top-level domain, XXX is the primary domain, and aa is the second-level domain.
By the way, what is a third-level domain name, the same method, www.aa.xxx.com.cn. There are three dots here, so it is a third-level domain name.
2. How to resolve the second-level domain name
The same domain name can be set to many resolutions, and each resolution can be mapped to a different IP address. For example, if there is a domain name xxx.cn, you can set www.xxx.cn to resolve to ip1, cs.xxx.cn to resolve to ip2, and so on.
The world.taobao.com mentioned at the beginning of the article uses the second-level domain name method, with the prefix world, to resolve world.taobao.com to an independent IP address.
3. What is the role of the second-level domain name
Some second-level domain names are used to distinguish between PC and M terminals, such as: vname.com and m.vname.com. The role of the second-level domain name is to separate from the main domain name, present different pages, and facilitate user viewing. It is also conducive to optimization. For example, different real estate projects across the country can be sub-stations. The second-level domain name is resolved under the main domain name. Problems with the second-level domain name will not affect the main domain name. Problems with the main domain name will definitely affect the second-level domain name.
4. Under what circumstances should a secondary domain name be used?
Secondary domain names are derived from primary domain names, also called subdomain names. A company can have many businesses, which is equivalent to establishing a new "business". This way, there is no need to register other domain names, which not only saves costs, but also creates a brand effect.
Or if the website traffic is large, it is necessary to open a branch site as an agent or operate it by yourself, such as loupan.com and cs.loupan.com (Changsha branch), which have hundreds of branches.
5. Summary
Secondary domain names do not need to be registered separately, and can be registered with the primary domain name. Secondary domain names can only be resolved from the primary domain name and cannot be applied for.
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