Adding a Security Group Rule

Scenarios

A security group consists of inbound and outbound rules. You can add security group rules to allow or deny the traffic to reach and leave the instances (such as ECSs) in the security group.

Security group rules allow or deny network traffic from specific sources over specific protocols or specific ports.

Precautions

• Before configuring security group rules, you need to plan access policies for instances in the security group. For details about common security group rules, see Security Group Examples.
• Add as fewer rules as possible. Notes and Constraints lists the constraints on the number of rules in a security group.
• After allowing traffic over a port in a security group rule, ensure that the port used by the instance is opened. For details, see Verifying Security Group Rules.
• If the source is set to 0.0.0.0/0 or::/0, then all external IP addresses are either allowed or denied to access your instances, depending on if the action is Allow or Deny. If the access is allowed, exposing high-risk ports, such as port 22, 3389, or 8848, to the public network will leave your instances vulnerable to network intrusions, service interruptions, data leakage, or ransomware attacks. You should only configure known IP addresses for the security group rule.
• By default, instances in the same security group can communicate with each other. If instances in the same security group cannot communicate with each other, possible causes are as follows:
  • The inbound rules for communications between these instances are deleted. Table 1 shows the inbound rules.

    Table 1 Inbound rules for communication between instances

    Direction	Priority	Action	Type	Protocol & Port	Source/Destination
    Inbound	1	Allow	IPv4	All	Source: current security group (Sg-A)
    Inbound	1	Allow	IPv6	All	Source: current security group (Sg-A)

  • Different VPCs cannot communicate with each other. The instances belong to the same security group but different VPCs.

    You can use VPC peering connections to connect VPCs in different regions.

Adding Rules to a Security Group

1. Log in to the management console.
2. Click in the upper left corner and select the desired region and project.
3. Click in the upper left corner and choose Networking > Virtual Private Cloud.

   The Virtual Private Cloud page is displayed.

4. In the navigation pane on the left, choose Access Control > Security Groups.

   The security group list is displayed.

5. Locate the target security group and click Manage Rules in the Operation column.

   The page for configuring security group rules is displayed.

6. On the Inbound Rules tab, click Add Rule.

   The Add Inbound Rule dialog box is displayed.

7. Configure required parameters.

   You can click to add more inbound rules.

   Figure 1 Add Inbound Rule
   

   Table 2 Inbound rule parameter description

   Parameter	Description	Example Value
   Priority	The security group rule priority. The priority value ranges from 1 to 100. The default value is 1 and has the highest priority. The security group rule with a smaller value has a higher priority.	1
   Action	The value can be Allow or Deny. If the Action is set to Allow, access from the source is allowed to ECSs in the security group over specified ports. If the Action is set to Deny, access from the source is denied to ECSs in the security group over specified ports. Security group rules are matched by priority and then by action. Deny rules take precedence over allow rules. For more information, see How Traffic Matches Security Group Rules.	Allow
   Type	Source IP address version. You can select: IPv4 IPv6	IPv4
   Protocol & Port	The network protocol used to match traffic in a security group rule. The protocol can be All, TCP, UDP, GRE, or ICMP.	TCP
   	Destination port used to match traffic in a security group rule. The value can be from 1 to 65535. Inbound rules control incoming traffic over specific ports to instances in the security group. Specify one of the following: Individual port: Enter a port, such as 22. Consecutive ports: Enter a port range, such as 22-30. Non-consecutive ports: Enter ports and port ranges, such as 22,23-30. You can enter a maximum of 20 ports and port ranges. Each port range must be unique. All ports: Leave it empty or enter 1-65535.	22, or 22-30
   Source	Used to match the IP address or address range of an external request. The source can be: IP address: You can enter multiple IP addresses, separated by commas (,). Each IP address defines a different security group rule. Single IP address: IP address/mask Example IPv4 address: 192.168.10.10/32 Example IPv6 address: 2002:50::44/128 IP address range in CIDR notation: IP address/mask Example IPv4 address range: 192.168.52.0/24 Example IPv6 address range: 2407:c080:802:469::/64 All IP addresses 0.0.0.0/0 represents all IPv4 addresses. ::/0 represents all IPv6 addresses. Security group: The source is from another security group. You can select a security group in the same region from the drop-down list. If there is instance A in security group A and instance B in security group B, and the inbound rule of security group A allows traffic from security group B, traffic is allowed from instance B to instance A. IP address group: An IP address group is a collection of one or more IP addresses. You can select an available IP address group from the drop-down list. An IP address group can help you manage IP address ranges and IP addresses with same security requirements in an easier way. If no IP address groups are available, create one by referring to Creating an IP Address Group.	IP address: 192.168.52.0/24,10.0.0.0/24
   Description	Supplementary information about the security group rule. This parameter is optional. The security group rule description can contain a maximum of 255 characters and cannot contain angle brackets (< or >).	N/A

8. Click OK.

   The inbound rule list is displayed.

9. On the Outbound Rules tab, click Add Rule.

   The Add Outbound Rule dialog box is displayed.

10. Configure required parameters.

    You can click to add more outbound rules.

    Figure 2 Add Outbound Rule
    

    Table 3 Outbound rule parameter description

    Parameter	Description	Example Value
    Priority	The security group rule priority. The priority value ranges from 1 to 100. The default value is 1 and has the highest priority. The security group rule with a smaller value has a higher priority.	1
    Action	The value can be Allow or Deny. If the Action is set to Allow, access from ECSs in the security group is allowed to the destination over specified ports. If the Action is set to Deny, access from ECSs in the security group is denied to the destination over specified ports. Security group rules are matched by priority and then by action. Deny rules take precedence over allow rules. For more information, see How Traffic Matches Security Group Rules.	Allow
    Type	Destination IP address version. You can select: IPv4 IPv6	IPv4
    Protocol & Port	The network protocol used to match traffic in a security group rule. The protocol can be All, TCP, UDP, GRE, or ICMP.	TCP
    	Destination port used to match traffic in a security group rule. The value can be from 1 to 65535. Outbound rules control outgoing traffic over specific ports from instances in the security group. Specify one of the following: Individual port: Enter a port, such as 22. Consecutive ports: Enter a port range, such as 22-30. Non-consecutive ports: Enter ports and port ranges, such as 22,23-30. You can enter a maximum of 20 ports and port ranges. Each port range must be unique. All ports: Leave it empty or enter 1-65535.	22, or 22-30
    Destination	Used to match the destination address of an internal request. The destination can be: IP address: You can enter multiple IP addresses, separated by commas (,). Each IP address defines a different security group rule. Single IP address: IP address/mask Example IPv4 address: 192.168.10.10/32 Example IPv6 address: 2002:50::44/128 IP address range in CIDR notation: IP address/mask Example IPv4 address range: 192.168.52.0/24 Example IPv6 address range: 2407:c080:802:469::/64 All IP addresses 0.0.0.0/0 represents all IPv4 addresses. ::/0 represents all IPv6 addresses. Security group: The destination is from another security group. You can select a security group in the same region under the current account from the drop-down list. If there is instance A in security group A and instance B in security group B, and the outbound rule of security group A allows traffic to security group B, traffic is allowed from instance A to instance B. IP address group: An IP address group is a collection of one or more IP addresses. You can select an available IP address group from the drop-down list. An IP address group can help you manage IP address ranges and IP addresses with same security requirements in an easier way. If no IP address groups are available, create one by referring to Creating an IP Address Group.	IP address: 192.168.52.0/24,10.0.0.0/24
    Description	Supplementary information about the security group rule. This parameter is optional. The security group rule description can contain a maximum of 255 characters and cannot contain angle brackets (< or >).	N/A

11. Click OK.

    The outbound rule list is displayed.

Verifying Security Group Rules

After allowing traffic over a port in a security group rule, you need to ensure that the port used by the instance is also opened.