Help Center/ Virtual Private Cloud/ User Guide (Kuala Lumpur Region)/ Getting Started/ Configuring a VPC for ECSs That Do Not Require Internet Access/ Step 2: Create a Subnet for the VPC
Updated on 2024-04-11 GMT+08:00
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Step 2: Create a Subnet for the VPC

Scenarios

A VPC comes with a default subnet. If the default subnet cannot meet your requirements, you can create one.

A subnet is configured with DHCP by default. When an ECS in this subnet starts, the ECS automatically obtains an IP address using DHCP.

Procedure

  1. Log in to the management console.
  1. Click in the upper left corner and choose Network > Virtual Private Cloud.

    The Virtual Private Cloud page is displayed.

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

    The Create Subnet page is displayed.

  4. Set the parameters as prompted.
    Table 1 Parameter descriptions

    Parameter

    Description

    Example Value

    VPC

    The VPC for which you want to create a subnet.

    -

    Name

    The subnet name.

    The name can contain a maximum of 64 characters, which may consist of letters, digits, underscores (_), hyphens (-), and periods (.). The name cannot contain spaces.

    Subnet

    IPv4 CIDR Block

    The CIDR block for the subnet. This value must be within the VPC CIDR block.

    192.168.0.0/24

    IPv6 CIDR Block

    Specifies whether to set IPv6 CIDR Block to Enable.

    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.

    -

    Associated Route Table

    The default route table to which the subnet will be associated. You can change the route table to a custom route table on the Subnets page.

    Default

    Gateway

    The gateway address of the subnet.

    This IP address is used to communicate with other subnets.

    192.168.0.1

    DNS Server Address

    DNS server addresses allow ECSs in a VPC subnet to communicate with each other using private domain names. You can also directly access cloud services through private DNS servers.

    If you want to use other public DNS servers for resolution, you can change the default DNS server addresses.

    A maximum of five DNS server IP addresses can be configured. Multiple IP addresses must be separated using commas (,).

    100.125.x.x

    NTP Server Address

    The IP address of the NTP server. This parameter is optional.

    You can configure the NTP server IP addresses to be added to the subnet as required. The IP addresses are added in addition to the default NTP server addresses. If you do not specify this parameter, no additional NTP server IP addresses will be added.

    192.168.2.1

    DHCP Lease Time
    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. Unit: Day or hour

    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.

    -

    Tag

    The subnet tag, which consists of a key and value pair. You can add a maximum of 10 tags to each subnet.

    The tag key and value must meet the requirements listed in Table 2.
    • Key: subnet_key1
    • Value: subnet-01

    Description

    Supplementary information about the subnet. This parameter is optional.

    The subnet description can contain a maximum of 255 characters and cannot contain angle brackets (< or >).

    -
    Table 2 Subnet tag key and value requirements

    Parameter

    Requirements

    Example Value

    Key
    • Cannot be left blank.
    • Must be unique for each subnet.
    • Can contain a maximum of 36 characters.
    • Can contain letters, digits, underscores (_), and hyphens (-).

    subnet_key1

    Value
    • Can contain a maximum of 43 characters.
    • Can contain letters, digits, underscores (_), periods (.), and hyphens (-).

    subnet-01
  5. Click OK.

Precautions

When a subnet is created, there are five reserved IP addresses, which cannot be used. For example, in a subnet with CIDR block 192.168.0.0/24, the following IP addresses are reserved:

  • 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: Gateway address.
  • 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.

If you configured the default settings under Advanced Settings during subnet creation, the reserved IP addresses may be different from the default ones, but there will still be five of them. The specific addresses depend on your subnet settings.