Help Center> Virtual Private Cloud> User Guide> Security> Security Group> Default Security Groups and Security Group Rules
View PDF

Default Security Groups and Security Group Rules

Your account automatically comes with a default security group (Sys-default). The default security group allows all outbound traffic, denies all inbound traffic, and allows all traffic between ECSs in the group. Your ECSs in this security group can communicate with each other already without adding additional rules.

Figure 1 shows the default security group.

Figure 1 Default security group
  • You cannot delete the default security group, but you can modify the rules for the default security group.
  • If two ECSs are in the same security group but in different VPCs, the ECSs cannot communicate with each other. To enable communications between the ECSs, use a VPC peering connection to connect the two VPCs first. For details about VPC connectivity, see Application Scenarios.

Table 1 describes the default rules for the default security group (Sys-default).

Table 1 Rules in the default security group (Sys-default)

Direction

Protocol

Port/Range

Source/Destination

Description

Outbound

All

All

Destination: 0.0.0.0/0

Allows all outbound traffic.

Inbound

All

All

Source: the current security group (for example, sg-xxxxx)

Allows communication among ECSs within the security group and denies all inbound traffic (incoming data packets).

Inbound

TCP

22

Source: 0.0.0.0/0

Allows all IP addresses to access Linux ECSs over SSH.

Inbound

TCP

3389

Source: 0.0.0.0/0

Allows all IP addresses to access Windows ECSs over RDP.
Parent topic: Security Group