Adding a Security Group Rule

A security group consists of inbound and outbound rules to control the traffic that is allowed to flow into or out of instances (such as ECSs) in the security group. Security group rules are commonly used to allow or deny network traffic from specific sources or over specific protocols, block certain ports, and define specific access permissions for instances.

Before adding a security group rule, note the following:

• A security group has inbound and outbound rules to control traffic that is allowed to reach or leave the instances associated with the security group. For details about the rules, see What Are Security Group Rules?.
• If an instance is associated with multiple security groups, the security group rules are matched by priority. For details about the matching sequence, see How Traffic Matches Security Group Rules.
• The number of rules in a security group is limited. Keep only the rules you need. For details, see Constraints on Using Security Groups.
• 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. For details, see Checking Whether a Port Is Enabled on an ECS.
• 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 instances are in the same VPC, but the inbound rules in the security group for communications between them are deleted. Table 1 shows the inbound rules.

    Table 1 Inbound rules for communications between instances in a security group

    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)

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

    You can use VPC peering connections to connect different VPCs. For details, see VPC Peering Connection Overview.

Before configuring security group rules, you need to plan access policies for instances in the security group.

• If an instance needs to provide services for external networks, add an inbound rule to allow external requests to the instance.
• If there are attacks to an instance from external networks, add an inbound rule to deny external requests that have security risks.
• If an instance needs to access external networks, add an outbound rule to allow requests from the instance to external networks.
• If you no longer need to control certain inbound or outbound traffic, you can delete the corresponding security group rules to simplify the rule configuration.

Security Group Examples shows more security group rule configuration examples.

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

   The VPC list page is displayed.

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

   The security group list is displayed.

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

   The page for configuring security group rules is displayed.

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

   The Add Inbound Rule dialog box is displayed.

6. Configure inbound rule parameters as prompted. You can add multiple inbound rules one by one.

   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, which 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, traffic is allowed to access the cloud servers in the security group over specified ports. If the Action is set to Deny, traffic is denied to access the cloud servers in the security group over specified ports.	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. Enter ports in any of the following formats: 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, 22-30
   Source	Source of the security group rule. The value can be IP address, Security group, or IP address group, to allow access from the IP addresses or the instances in the security group. IP address Single IP address: 192.168.10.10/32 (IPv4); 2002:50::44/128 (IPv6) Any IP address: 0.0.0.0/0 (IPv4); ::/0 (IPv6) IP address range: 192.168.1.0/24 (IPv4); 2407:c080:802:469::/64 (IPv6) IP address group: ipGroup-A If the source is a security group, this rule will apply to all instances associated with the selected security group.	192.168.0.0/24
   Description	(Optional) Supplementary information about the security group rule. The security group rule description can contain a maximum of 255 characters and cannot contain angle brackets (< or >).	N/A

7. Click OK.

   The inbound rule list is displayed.

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

   The Add Outbound Rule dialog box is displayed.

9. Configure outbound rule parameters as prompted. You can add multiple outbound rules one by one.

   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, which 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.	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. Enter ports in any of the following formats: 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, 22-30
   Destination	Destination of the security group rule. The value can be IP address, Security group, or IP address group, to allow access to the IP addresses or the instances in the security group. IP address Single IP address: 192.168.10.10/32 (IPv4); 2002:50::44/128 (IPv6) Any IP address: 0.0.0.0/0 (IPv4); ::/0 (IPv6) IP address range: 192.168.1.0/24 (IPv4); 2407:c080:802:469::/64 (IPv6) IP address group: ipGroup-A	0.0.0.0/0
   Description	(Optional) Supplementary information about the security group rule. The security group rule description can contain a maximum of 255 characters and cannot contain angle brackets (< or >).	N/A

10. Click OK.

    The outbound rule list is displayed.

    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. For details, see Checking Whether a Port Is Enabled on an ECS.

1. Log in to the management console.

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

   The VPC list page is displayed.

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

   The security group list is displayed.

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

   The page for configuring security group rules is displayed.

5. On the Inbound Rules tab, click Fast-Add Rule.

   The Fast-Add Inbound Rule dialog box is displayed.

6. Configure inbound rule parameters as prompted.

   Table 4 Inbound rule parameter description

   Parameter	Description	Example Value
   Protocols and Ports	Common protocols and ports are provided for: Remote login and ping Web service Database	SSH (22)
   Type	Source IP address version. You can select: IPv4 IPv6	IPv4
   Source	Source of the security group rule. The value can be IP address, IP address group, or Security group to allow access from the IP addresses or the instances in the security group. You can specify: A single IP address: 192.168.10.10/32 (IPv4); 2002:50::44/127 (IPv6) An IP address range: 192.168.1.0/24 (IPv4); 2407:c080:802:469::/64 (IPv6) Any IP address: 0.0.0.0/0 (IPv4); ::/0 (IPv6) Security group: sg-abc IP address group: ipGroup-test If the source is a security group, this rule will apply to all instances associated with the selected security group.	192.168.0.0/24
   Action	The value can be Allow or Deny. If the Action is set to Allow, traffic is allowed to access the cloud servers in the security group over specified ports. If the Action is set to Deny, traffic is denied to access the cloud servers in the security group over specified ports.	Allow
   Priority	The security group rule priority. The priority value ranges from 1 to 100. The default value is 1, which has the highest priority. The security group rule with a smaller value has a higher priority.	1
   Description	(Optional) Supplementary information about the security group rule. The security group rule description can contain a maximum of 255 characters and cannot contain angle brackets (< or >).	N/A

7. Click OK.

   The inbound rule list is displayed and you can view your added rule.

8. On the Outbound Rules tab, click Fast-Add Rule.

   The Fast-Add Outbound Rule dialog box is displayed.

9. Configure outbound rule parameters as prompted.

   Table 5 Outbound rule parameter description

   Parameter	Description	Example Value
   Protocols and Ports	Common protocols and ports are provided for: Remote login and ping Web service Database	SSH (22)
   Type	Destination IP address version. You can select: IPv4 IPv6	IPv4
   Destination	Destination of the security group rule. The value can be IP address, IP address group, or Security group to allow access to the IP addresses or the instances in the security group. You can specify: xxx.xxx.xxx.xxx/32 (IPv4 address) xxx.xxx.xxx.0/24 (IPv4 address range) 0.0.0.0/0 (any IPv4 address) sg-abc (security group) IP address group: ipGroup-test	0.0.0.0/0
   Priority	The security group rule priority. The priority value ranges from 1 to 100. The default value is 1, which 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.	Allow
   Description	(Optional) Supplementary information about the security group rule. The security group rule description can contain a maximum of 255 characters and cannot contain angle brackets (< or >).	N/A

10. Click OK.

    The outbound rule list is displayed and you can view your added rule.

    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. For details, see Checking Whether a Port Is Enabled on an ECS.

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

   The VPC list page is displayed.

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

   The security group list is displayed.

4. Locate the target security group and click its name.

   The security group details page is displayed.

5. Click the Inbound Rules or Outbound Rules tab as required, and then click Allow Common Ports.

   The Allow Common Ports page is displayed.

   Table 6 describes the common ports that can be opened with a few clicks.

   Table 6 Common ports

   Direction	Protocol & Port & Type	Source/Destination	Description
   Inbound	TCP: 22 (IPv4)	0.0.0.0/0	Allows all IPv4 addresses to access ECSs in the security group over port 22 (SSH) for remotely logging in to Linux ECSs.
   	TCP: 3389 (IPv4)	0.0.0.0/0	Allows all IPv4 addresses to access ECSs in the security group over port 3389 (RDP) for remotely logging in to Windows ECSs.
   	TCP: 80 (IPv4)	0.0.0.0/0	Allows all IPv4 addresses to access ECSs in the security group over port 80 (HTTP) for visiting websites.
   	TCP: 443 (IPv4)	0.0.0.0/0	Allows all IPv4 addresses to access ECSs in the security group over port 443 (HTTPS) for visiting websites.
   	TCP: 20-21 (IPv4)	0.0.0.0/0	Allows all IPv4 addresses to access ECSs in the security group over ports 20 and 21 (FTP) for uploading or downloading files.
   	ICMP: All (IPv4)	0.0.0.0/0	Allows all IPv4 addresses to access ECSs in the security group over any port for using the ping command to test ECS connectivity.
   Outbound	All (IPv4) All (IPv6)	0.0.0.0/0 ::/0	Allows access from ECSs in the security group to any IP address over any port.

6. Click OK.

   After the operation is complete, you can view the added rules in the security group rule list.

   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. For details, see Checking Whether a Port Is Enabled on an ECS.

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.

For example, if you have deployed a website on an ECS and want users to access your website through HTTP (80), you need to add an inbound rule to the ECS security group to allow access over the port. Table 7 shows the rule.

After adding the security group rule, perform the following operations to check whether the ECS port is opened and whether the rule is applied:

1. Log in to the ECS and check whether the ECS port is enabled.
   • Checking a Linux ECS port

     Run the following command to check whether TCP port 80 is being listened on:

     netstat -an | grep 80

     If the following figure is displayed, TCP port 80 is enabled.

     Figure 1 Command output for the Linux ECS

     
     
   • Checking a Windows ECS port
     1. Choose Start > Run. Type cmd to open the Command Prompt.
     2. Run the following command to check whether TCP port 80 is being listened on:

        netstat -an | findstr 80

        If the following figure is displayed, TCP port 80 is enabled.

        Figure 2 Command output for the Windows ECS

        
        
2. Enter http://ECS EIP in the address box of the browser and press Enter.

   If the requested page can be accessed, the security group rule has taken effect.