Configuring ISP Lines

Background

Usually, a DNS server returns the same IP address to visitors from different networks. However, in cross-network access, this would lead to high latency and poor user experience.

If you configure ISP lines when you create record sets, the DNS server returns different resolution results or IP addresses to visitors based on their carrier networks.

ISP lines can be configured only for public zones.

If a resolution line is faulty, you cannot switch to another resolution line.

For example, you have built a website using domain name example.com and hosted the website on three servers, with one in a China Telecom equipment room, one in a China Unicom data center, and one in a China Mobile data center. You need to configure four ISP lines: Default, China Telecom, China Unicom, and China Mobile.

ISP Lines

ISP lines are categorized by telecom carriers in China.

**Table 1** ISP lines
Level 1	Level 2	Level 3
China Telecom, China Mobile, China Unicom, Jiaoyuwang, Pengboshi, and Tietong	North China	Beijing, Tianjin, Hebei, Shanxi, and Inner Mongolia
	Northeast China	Liaoning, Jilin, and Heilongjiang
	Northwest China	Shaanxi, Gansu, Qinghai, Ningxia, and Xinjiang
	Central China	Henan, Hubei, and Hunan
	East China	Shanghai, Jiangsu, Zhejiang, Anhui, Fujian, Jiangxi, and Shandong
	South China	Guangdong, Hainan, and Guangxi
	Southwest China	Chongqing, Sichuan, Guizhou, Yunnan, and Tibet

For example, you have configured the following resolution lines for record set example.com:

Default: 1.1.1.1
China Telecom: 2.2.2.2
China Telecom_North China: 3.3.3.3

When a China Telecom user in North China requests the domain name example.com, IP address 3.3.3.3 is returned. When a China Telecom user in another region requests this domain name, IP address 2.2.2.2 is returned. When a non-China Telecom user in a region other than North China requests the domain name, IP address 1.1.1.1 is returned.

Procedure

Configure ISP lines for your public domain names hosted on the DNS service.

The following example describes how to configure the record set of the Default line to 1.1.1.1 and the record set of the China Telecom line to 2.2.2.2 for example.com.

Log in to the management console.
Hover the cursor over in the upper left corner. In the service list, choose Networking > Domain Name Service.
The DNS console is displayed.
In the navigation pane on the left, choose Public Zones.
The Public Zones page is displayed.

Click the name (example.com) of the public zone.
The Record Sets page is displayed.
Click Add Record Set.
Figure 1 Add Record Set

Add two A record sets for example.com. Set the parameters based on Table 2.

**Table 2** Parameters for adding an A record set
Parameter	Description	Line 1	Line 2
Name	Prefix of the domain name to be resolved. For example, if the domain name is example.com, the prefix can be as follows: www: The domain name is www.example.com, which is usually used for a website. Left blank: The domain name is example.com. In some cases, you may need to set the record set name to the at sign (@). However, the at sign is not supported. Leave the Name blank. abc: The domain name is abc.example.com, a subdomain of example.com. mail: The domain name is mail.example.com, which is typically used for an email server. : The domain name is .example.com, which is a wildcard domain name, indicating all subdomains of example.com.	www	www
Type	Type of the record set.	A – Map domains to IPv4 addresses	A – Map domains to IPv4 addresses
Line	Resolution line. The DNS server will return the IP address of the specified line, depending on where the visitors come from. Default: returns the default resolution result irrespective of where the visitors come from. ISP: returns the resolution result based on visitors' carrier networks. Region: returns the resolution result based on visitors' geographical locations. For details, see Configuring Region Lines.	Default	ISP_China Telecom
TTL (s)	Cache duration of the record set on a local DNS server, in seconds. The value ranges from 300 to 2147483647, and the default is 300. If your service address changes frequently, set TTL to a smaller value. Learn more about TTL.	The default value is 300s, which is, 5 minutes.	The default value is 300s, which is, 5 minutes.
Value	IPv4 addresses mapped to the domain name. Enter each IPv4 address on a separate line.	1.1.1.1	2.2.2.2
Weight	(Optional) Weight of a record set. The value ranges from 0 to 1000, and the default value is 1. This parameter is supported only for public domain names. If a resolution line in a zone contains multiple record sets of the same type, you can set different weights to each record set. For details, see Configuring Weighted Routing.	1	1
Tag	(Optional) Identifier of the record set. This parameter is displayed when you expand More Settings. Each tag contains a key and a value. You can add a maximum of 10 tags to a record set. For details about tag key and value requirements, see Table 3.	example_key1 example_value1	example_key1 example_value1
Description	(Optional) Supplementary information about the record set. You can enter a maximum of 255 characters.	N/A	N/A

**Table 3** Tag key and value requirements
Parameter	Requirements	Example Value
Key	Cannot be left blank. Must be unique for each resource. Can contain a maximum of 36 characters. Cannot start or end with a space or contain special characters =*<>\,\|/	example_key1
Value	Cannot be left blank. Can contain a maximum of 43 characters. Cannot start or end with a space or contain special characters =*<>\,\|/	example_value1