Security Group Configuration Examples

Here are some common security group configuration examples for different scenarios, including remote login to ECSs, website access, and internal communication between instances in different security groups.

Generally, a security group denies all external requests by default. You need to add inbound rules to a security group based on the whitelist principle to allow specific external requests to access instances in the security group.

By default, all outbound rules of a security group allow all requests from instances in the security group to access external networks. Table 1 lists the rules.

Table 1 Default outbound rules in a security group

Direction

Type

Protocol & Port

Destination

Description

Outbound

IPv4

All

0.0.0.0/0

This rule allows access from instances in the security group to any IPv4 address over any port.

Outbound

IPv6

All

::/0

This rule allows access from instances in the security group to any IPv6 address over any port.

Remotely Logging In to an ECS from a Local Server

A security group denies all external requests by default. To remotely log in to an ECS from a local server, add an inbound security group rule based on the OS running on the ECS.

  • To remotely log in to a Linux ECS using SSH, enable the SSH (22) port. For details, see Table 2.

  • To remotely log in to a Windows ECS using RDP, enable the RDP (3389) port. For details, see Table 3.

    Table 2 Remotely logging in to a Linux ECS using SSH

    Direction

    Type

    Protocol & Port

    Source

    Inbound

    IPv4

    TCP: 22

    IP address: 0.0.0.0/0

    Table 3 Remotely logging in to a Windows ECS using RDP

    Direction

    Type

    Protocol & Port

    Source

    Inbound

    IPv4

    TCP: 3389

    IP address: 0.0.0.0/0

    Important

    If the source is set to 0.0.0.0/0, remotely logging in to the ECS through any IP address is allowed. To ensure security, set the source to a specific IP address based on service requirements. For details about the configuration example, see Table 4.

    Table 4 Remotely logging in to an ECS using a specified IP address

    ECS Type

    Direction

    Type

    Protocol & Port

    Source

    Linux ECS

    Inbound

    IPv4

    TCP: 22

    IP address: 192.168.0.0/24

    Windows ECS

    Inbound

    IPv4

    TCP: 3389

    IP address: 10.10.0.0/24

Remotely Connecting to an ECS from a Local Server to Upload or Download Files

By default, a security group denies all external requests. If you need to remotely connect to an ECS from a local server to upload or download files, you need to enable FTP ports 20 and 21.

Table 5 Remotely connecting to an ECS from a local server to upload or download files

Direction

Type

Protocol & Port

Source

Inbound

IPv4

TCP: 20-21

IP address: 0.0.0.0/0

Important

You must first install the FTP server program on the ECSs and check whether ports 20 and 21 are working properly.

Setting Up a Website on an ECS to Provide Services Externally

A security group denies all external requests by default. If you have set up a website on an ECS that can be accessed externally, you need to add an inbound rule to the ECS security group to allow access over specific ports, such as HTTP (80) and HTTPS (443).

Table 6 Setting up a website on an ECS to provide services externally

Direction

Type

Protocol & Port

Source

Inbound

IPv4

TCP: 80

IP address: 0.0.0.0/0

Inbound

IPv4

TCP: 443

IP address: 0.0.0.0/0

Using ping Command to Verify Network Connectivity

By default, a security group denies all external requests. If you need to run the ping command on an ECS to verify network connectivity, add an inbound rule to the ECS security group to allow access over the ICMP port.

Table 7 Using ping command to verify network connectivity

Direction

Type

Protocol & Port

Source

Inbound

IPv4

ICMP: All

IP address: 0.0.0.0/0

Inbound

IPv6

ICMP: All

IP address: ::/0

Enabling ECSs In Different Security Groups to Communicate Through an Internal Network

ECSs in the same VPC but associated with different security groups cannot communicate with each other. If you want to share data between ECSs in a VPC, for example, ECSs in security group sg-A need to access MySQL databases in security group sg-B, you need to add an inbound rule to security group sg-B to allow access from ECSs in security group sg-A over MySQL port 3306.

Table 8 Enabling instances in different security groups to communicate through an internal network

Direction

Type

Protocol & Port

Source

Inbound

IPv4

TCP: 3306

Security group: sg-A

ECS Providing Database Access Service

A security group denies all external requests by default. If you have deployed the database service on an ECS and need to allow other ECSs to access the database service through an internal network, you need to add an inbound rule to the security group of the ECS with the database service deployed to allow access over ports, for example, MySQL (3306), Oracle (1521), MS SQL (1433), PostgreSQL (5432) and Redis (6379).

Table 9 ECS providing database access service

Direction

Type

Protocol & Port

Source

Description

Inbound

IPv4

TCP: 3306

Security group: sg-A

This rule allows ECSs in security group sg-A to access the MySQL database service.

Inbound

IPv4

TCP: 1521

Security group: sg-B

This rule allows ECSs in security group sg-B to access the Oracle database service.

Inbound

IPv4

TCP: 1433

IP address: 172.16.3.21/32

This rule allows the ECS whose private IP address is 172.16.3.21 to access the MS SQL database service.

Inbound

IPv4

TCP: 5432

IP address: 192.168.0.0/24

This rule allows ECSs whose private IP addresses are in the 192.168.0.0/24 network to access the PostgreSQL database service.

Important

In this example, the source is for reference only. Set the source address based on actual requirements.

Allowing ECSs to Access Only Specific External Websites

By default, a security group allows all outbound traffic. Table 11 lists the default rules. If you want to allow ECSs to access only specific websites, configure the security groups of the ECSs as follows:

  1. First, add outbound rules to allow traffic over specific ports and to specific IP addresses.

    Table 10 Enabling instances in different security groups to communicate through an internal network

    Direction

    Type

    Protocol & Port

    Source

    Outbound

    IPv4

    TCP: 80

    IP address: 132.15.XX.XX

    Outbound

    IPv4

    TCP: 443

    IP address: 145.117.XX.XX

  2. Then, delete the original outbound rules that allow all traffic shown in Table 11.

    Table 11 Default outbound rules in a security group

    Direction

    Type

    Protocol & Port

    Destination

    Description

    Outbound

    IPv4

    All

    0.0.0.0/0

    This rule allows access from instances in the security group to any IPv4 address over any port.

    Outbound

    IPv6

    All

    ::/0

    This rule allows access from instances in the security group to any IPv6 address over any port.