Configuring Security Group Rules for Backend Servers¶
Scenarios¶
When you add a backend server to a backend server group, ensure that the rules of the security group that containing the backend server allows access from the VPC where the backend server resides, and that the destination port is that used by the backend server. You also need to configure the protocol and port used for health checks. If you use UDP for health checks, configure inbound rules to allow ICMP traffic. Otherwise, health checks cannot be performed on the added backend server.
If you have no VPCs when creating a server, the system will automatically create a VPC with default security rules. Default security group rules allow only communications among the servers in the VPC. You also need to configure inbound rules to enable the load balancer to communicate with these servers over the frontend port and health check port.
Caution
Load balancers: If Cross-VPC Backend is not enabled for a load balancer that has a TCP or UDP listener, there is no need to configure security group rules and Firewall rules to allow traffic from the VPC where the load balancer works to the backend servers.
Procedure¶
Log in to the management console.
In the upper left corner of the page, click
and select the desired region and project.Hover on
in the upper left corner to display Service List and choose Computing > Elastic Cloud Server.In the ECS list, locate the ECS and click its name.
The ECS details page is displayed.
Click Security Groups, locate the security group, and view security group rules.
Click the security group rule ID or Modify Security Group Rule. The security group details page is displayed.
Under Inbound Rules, click Add Rule.
TCP, HTTP, or HTTPS listeners
If the health check port is not the one used by each backend server, add an inbound rule to allow TCP traffic over the health check port and the ports used by backend servers.
If you do not specify a health check port, add inbound rules to allow TCP traffic over the ports used by backend servers.
To ensure normal health checks, ensure that security group rules allow traffic from the CIDR block of the subnet where the load balancer resides and traffic from the health check port and from the ports used by backend servers.
UDP listeners
If the health check port is not the one used by each backend server, add an inbound rule to allow UDP traffic over the health check port and the ports used by backend servers.
If you do not specify a health check port, add inbound rules to allow UDP traffic over the ports used by backend servers.
To ensure normal health checks, ensure that security group rules allow traffic from the CIDR block of the subnet where the load balancer resides and traffic from the health check port and from the ports used by backend servers.
You need also to add an inbound rule to allow ICMP traffic.
Click OK.
Configuring Firewall Rules¶
To control traffic in and out of a subnet, you can associate a firewall with the subnet. Similar to security groups, firewalls control access to subnets and add an additional layer of defense to your subnets. Default firewall rules reject all inbound and outbound traffic. If the subnet of a load balancer or associated backend servers has a firewall associated, the load balancer cannot receive traffic from the Internet or route traffic to backend servers, and backend servers cannot receive traffic from and respond to the load balancer.
Configure an inbound firewall rule to allow traffic from the VPC where the load balancer works to backend servers.
Caution
Load balancer: If Cross-VPC Backend is not enabled for a load balancer that has a TCP or UDP listener, there is no need to configure security group rules and firewall rules to allow traffic from the VPC where the load balancer works to the backend servers associated with TCP or UDP listener.
Log in to the management console.
In the upper left corner of the page, click
and select the desired region and project.Hover on
in the upper left corner to display Service List and choose Network > Virtual Private Cloud.In the navigation pane on the left, choose Firewall.
In the firewall list, click the name of the firewall to switch to the page showing its details.
On the Inbound Rules or Outbound Rules tab page, click Add Rule to add a rule.
Action: Select Allow.
Protocol: The protocol must be the same as the one you selected for the listener.
Source: Set it to the VPC CIDR block.
Source Port Range: Select a port range.
Destination: If you keep the default value, 0.0.0.0/0, traffic will be allowed for all destination IP addresses.
Destination Port Range: Select a port range.
(Optional) Description: Describe the firewall rule.
Click OK.