Step 2: Create a Subnet for the VPC

Scenarios

Procedure

1. Log in to the management console.

2. Click in the upper left corner and choose Network > Virtual Private Cloud.

   The Virtual Private Cloud page is displayed.

3. In the navigation pane on the left, choose Virtual Private Cloud > Subnets.
4. Click Create Subnet.

   The Create Subnet page is displayed.

5. Set the subnet parameters as needed.

   You can click to create more subnets. A maximum of three subnets can be created at a time.

   Table 1 Subnet parameter descriptions

   Parameter	Description	Example Value
   VPC	The VPC for which you want to create a subnet.	vpc-test
   Name	The subnet name. The name: Can contain 1 to 64 characters. Can contain letters, digits, underscores (_), hyphens (-), and periods (.).	subnet-01
   IPv4 CIDR Block	A subnet is a unique CIDR block with a range of IP addresses in a VPC. Comply with the following principles when planning subnets: Planning CIDR block size: After a subnet is created, the CIDR block cannot be changed. You need to properly plan the CIDR block in advance based on the number of IP addresses required by your service. The subnet CIDR block size cannot be too small. Ensure that the number of available IP addresses in the subnet meets service requirements. Remember that the first and last three addresses in a subnet CIDR block are reserved for system use. For example, in subnet 10.0.0.0/24, 10.0.0.1 is the gateway address, 10.0.0.253 is the system interface address, 10.0.0.254 is used by DHCP, and 10.0.0.255 is the broadcast address. The subnet CIDR block cannot be too large, either. If you use a CIDR block that is too large, you may not have enough CIDR blocks available later for new subnets, which can be a problem when you want to scale out services. Avoid CIDR block conflicts if you need to connect two VPCs or connect a VPC to an on-premises data center.	10.0.0.0/24
   IPv6 CIDR Block (Optional)	If you select this option, the system automatically assigns an IPv6 CIDR block to the created subnet. Currently, the IPv6 CIDR block cannot be customized. IPv6 cannot be disabled after the subnet is created.	N/A
   Associated Route Table	The default route table with which the subnet will be associated. A route table contains a set of routes that are used to control the traffic routing for your subnets in a VPC. Each VPC comes with a default route table. Subnets in the VPC are then automatically associated with the default route table. The default route table ensures that subnets in a VPC can communicate with each other.	N/A
   Advanced Settings (Optional) > Gateway	The gateway address of the subnet. Click to expand the configuration area and set this parameter. Retain the default value unless there are special requirements.	10.0.0.1
   Advanced Settings (Optional) > DNS Server Address	The DNS server addresses. Click to expand the configuration area and set this parameter. By default, two DNS server addresses are configured. You can change them if necessary. Multiple IP addresses must be separated using commas (,). NOTE: Changing the default DNS server addresses may cause communication failures in the subnet.	100.125.x.x
   Advanced Settings (Optional) > Domain Name	The domain name. Click to expand the configuration area and set this parameter. Enter domain names (), separated with spaces. A maximum of 254 characters are allowed. A domain name can consist of multiple labels (max. 63 characters each). To access a domain name, you only need to enter the domain name prefix. ECSs in the subnet automatically match the configured domain name suffix. If the domain names are changed, ECSs newly added to this subnet will use the new domain names. If an existing ECS in this subnet needs to use the new domain names, restart the ECS or run a command to restart the DHCP Client service or network service.	test.com
   Advanced Settings (Optional) > NTP Server Address	The IP address of the NTP server. Click to expand the configuration area and set this parameter. If you want to add NTP server addresses for a subnet, you can specify NTP Server Address. The IP addresses are added in addition to the default NTP server addresses. If you add or change the NTP server addresses of a subnet, you need to renew the DHCP lease for or restart all the ECSs in the subnet to make the change take effect immediately. If the NTP server addresses have been cleared out, restarting the ECSs will not help. You must renew the DHCP lease for all ECSs to make the change take effect immediately.	192.168.2.1
   Advanced Settings (Optional) > IPv4 DHCP Lease Time	The period during which a client can use an IP address automatically assigned by the DHCP server. Click to expand the configuration area and set this parameter. The period during which a client can use an IP address automatically assigned by the DHCP server. After the lease time expires, a new IP address will be assigned to the client. If the time period is changed, the new lease time takes effect when the instance (such as an ECS) in the subnet is renewed next time. You can wait for the instance to be renewed automatically or manually modify the lease time. If you want the new lease time to take effect immediately, manually renew the lease or restart the ECS.	N/A
   Advanced Settings (Optional) > Tag	The subnet tag. Click to expand the configuration area and set this parameter. Add tags to help you quickly identify, classify, and search for your subnets. For details, see Managing Subnet Tags.	Key: subnet_key1 Value: subnet-01
   Advanced Settings > Description	Supplementary information about the subnet. Click to expand the configuration area and set this parameter. Enter the description about the subnet in the text box as required. The subnet description can contain a maximum of 255 characters and cannot contain angle brackets (< or >).	N/A

6. Click Create Now.

   Return to the subnet list and view the new subnet.

Notes and Constraints

• 192.168.0.0: Network ID. This address is the beginning of the private IP address range and will not be assigned to any instance.
• 192.168.0.1: The gateway address of the subnet.
• 192.168.0.253: Reserved for the system interface. This IP address is used by the VPC for external communication.
• 192.168.0.254: DHCP service address.
• 192.168.0.255: Network broadcast address.