- What's New
- Function Overview
-
Service Overview
- What Is ELB?
- Product Advantages
- How ELB Works
- Application Scenarios
- Differences Between Dedicated and Shared Load Balancers
- Load Balancing on a Public or Private Network
- Network Traffic Paths
- Specifications of Dedicated Load Balancers
- Quotas and Constraints
- Billing (Dedicated Load Balancers)
- Permissions
- Product Concepts
- How ELB Works with Other Services
- Change History
- Getting Started
-
User Guide
-
Load Balancer
- Overview
- Preparations for Creating a Load Balancer
- Creating a Dedicated Load Balancer
- Creating a Shared Load Balancer
- Modifying the Bandwidth
- Changing the Specifications of a Dedicated Load Balancer
- Changing an IP Address
- Binding an IP Address to or Unbinding an IP Address from a Load Balancer
- Adding to or Removing from an IPv6 Shared Bandwidth
- Enabling or Disabling a Load Balancer
- Exporting the Load Balancer List
- Deleting a Load Balancer
- Listener
- Advanced Features of HTTP/HTTPS Listeners
- Backend Server Group
- Backend Server (Dedicated Load Balancers)
- Backend Server (Shared Load Balancers)
- Certificate
- Access Control
- TLS Security Policy
- Tag
- Access Logging
- Monitoring
- Auditing
- Permissions Management
- Quotas
- Appendix
- Change History
-
Load Balancer
- Best Practices
-
API Reference
- Before You Start
- API Overview
- Calling APIs
- APIs (V3)
- Examples
- Permissions and Supported Actions
- Appendix
- SDK Reference
-
FAQs
- Popular Questions
-
ELB Use
- Service Abnormality
-
ELB Functionality
- Can ELB Be Used Separately?
- Does ELB Support Persistent Connections?
- Does ELB Support FTP on Backend Servers?
- Can ELB Block DDoS Attacks and Secure Web Code?
- Is an EIP Assigned Exclusively to a Load Balancer?
- How Many Load Balancers and Listeners Can I Have?
- What Types of APIs Does ELB Provide? What Are Permissions of ELB?
- Can I Adjust the Number of Backend Servers When a Load Balancer is Running?
- Can Backend Servers Run Different OSs?
- Can I Configure Different Backend Ports for a Load Balancer?
- Are There Any Restrictions on the Frequency of Access from an IP Address?
- Can ELB Be Used Across Accounts or VPCs?
- Can Backend Servers Access the Ports of a Load Balancer?
- Can I Bind a Public IP Address Purchased from a Third-Party Cloud Provider to My Load Balancer?
- Can Both the Listener and Backend Server Group Use HTTPS?
- Can I Change the VPC and Subnet for My Load Balancer?
- Does ELB Support IPv6 Networks?
- Load Balancing Performance
-
Load Balancers
- What Is Quota?
- How Does ELB Distribute Traffic?
- How Can I Access a Load Balancer Across VPCs?
- How Can I Configure Load Balancing for Containerized Applications?
- Why Can't I Delete My Load Balancer?
- Do I Need to Configure Bandwidth for My Load Balancers?
- Can I Bind Multiple EIPs to a Load Balancer?
- Why Multiple IP Addresses Are Required When I Create or Enable a Load Balancer?
- Why Are Requests from the Same IP Address Routed to Different Backend Servers When the Load Balancing Algorithm Is Source IP Hash?
- Can Backend Servers Access the Internet Using the EIP of the Load Balancer?
- Will Traffic Routing Be Interrupted If the Load Balancing Algorithm Is Changed?
- What Is the Difference Between the Bandwidth Included in Each Specification of a Dedicated Load Balancer and the Bandwidth of an EIP?
- How Do I Combine ELB and WAF?
-
Listeners
- What Are the Relationships Between Load Balancing Algorithms and Sticky Session Types?
- Can I Bind Multiple Certificates to a Listener?
- Do HTTP and HTTP Listeners Support the X-Forwarded-Host Header?
- Will ELB Stop Distributing Traffic Immediately After a Listener Is Deleted?
- Does ELB Have Restrictions on the File Upload Speed and Size?
- Can Multiple Load Balancers Route Requests to One Backend Server?
- How Is WebSocket Used?
- What Are the Three Timeouts of a Listener and What Are the Default Durations?
- Why Can't I Select the Target Backend Server Group When Adding or Modifying a Listener?
- Why Cannot I Add a Listener to a Dedicated Load Balancer?
-
Backend Servers
- Why Is the Interval at Which Backend Servers Receive Health Check Packets Different from What I Have Configured?
- Can Backend Servers Access the Internet After They Are Associated with a Load Balancer?
- Can ELB Distribute Traffic Across Servers That Are Not Provided by Huawei Cloud?
- Can ELB Route Traffic Across Regions?
- Does Each Backend Server Need an EIP to Receive Requests from a Public Network Load Balancer?
- How Do I Check the Network Conditions of a Backend Server?
- How Can I Check the Network Configuration of a Backend Server?
- How Do I Check the Status of a Backend Server?
- How Long Is the Timeout Duration of Connections Between a Load Balancer and Backend Servers?
- When Is a Backend Server Considered Healthy?
- How Do I Check Whether a Backend Server Can Be Accessed Through an EIP?
- Why Is the Number of Active Connections Monitored by Cloud Eye Different from the Number of Connections Established with the Backend Servers?
- Why Can I Access Backend Servers After a Whitelist Is Configured?
- When Will Modified Weights Take Effect?
- How Much Time Is Required for a Load Balancer to Disconnect from Backend Servers After The Servers Are Removed?
- Why Must the Subnet Where the Load Balancer Resides Have at Least 16 Available IP Addresses for Enabling IP as a Backend?
-
Health Checks
- How Do I Troubleshoot an Unhealthy Backend Server?
- Why Is the Interval at Which Backend Servers Receive Health Check Packets Different from the Configured Interval?
- How Does ELB Perform UDP Health Checks? What Are the Precautions for UDP Health Checks?
- Why Does ELB Frequently Send Requests to Backend Servers During Health Checks?
- When Does a Health Check Start?
- Do Maximum Retries Include Health Checks That Consider Backend Servers Unhealthy?
- What Do I Do If a Lot of Access Logs Are Generated During Health Checks?
- What Status Codes Will Be Returned If Backend Servers Are Identified as Healthy?
- Obtaining Source IP Addresses
-
HTTP/HTTPS Listeners
- Which Protocol Should I Select for the Backend Server Group When Adding an HTTPS Listener?
- Why Is There a Security Warning After a Certificate Is Configured?
- Why Is a Forwarding Policy in the Faulty State?
- Why Can't I Add a Forwarding Policy to a Listener?
- Why Cannot I Select an Existing Backend Server Group When Adding a Forwarding Policy?
- Sticky Sessions
- Certificates
- Monitoring
- Billing
- Videos
Security Group Rules
To ensure normal communications between the load balancer and backend servers, you need to check the security group rules and network ACL rules configured for the backend servers.
When backend servers receive requests from the load balancer, source IP addresses are translated into those in 100.125.0.0/16.
- Security group rules must allow traffic from the 100.125.0.0/16 to backend servers. For details about how to configure security group rules, see Configuring Security Group Rules.
- Network ACL rules are optional for subnets. If network ACL rules are configured for the backend subnet of the load balancer, the network ACL rules must allow traffic from the backend subnet of the load balancer to the backend servers. For details about how to configure these rules, see Configuring Network ACL Rules.
If Transfer Client IP Address is enabled for the TCP or UDP listeners, network ACL rules and security group rules will not take effect. You can use access control to limit which IP addresses are allowed to access the listener. Learn how to configure access control.
Constraints and Limitations
- If health check is enabled for a backend server group, security group rules must allow traffic from the health check port over the health check protocol.
- If UDP is used for health check, there must be a rule that allows ICMP traffic. If there is no such rule, the health of the backend servers cannot be checked.
Configuring Security Group Rules
If you have no VPCs when creating a server, the system automatically creates one for you. Default security group rules allow only communications among the servers in the VPC. To ensure that the load balancer can communicate with these servers over both the frontend port and health check port, configure inbound rules for security groups containing these servers.
- Log in to the management console.
- In the upper left corner of the page, click
and select the desired region and project.
- Under Compute, click Elastic Cloud Server.
- On the Elastic Cloud Server page, click the name of the ECS that has been added to a backend server group.
The page providing details about the ECS is displayed.
- Click Security Groups, locate the security group, and view security group rules.
- Click the ID of a security group rule or Modify Security Group Rule. The security group details page is displayed.
- On the Inbound Rules tab page, click Add Rule. Configure an inbound rule based on Table 1.
Table 1 Security group rules Backend Protocol
Policy
Protocol & Port
Source IP Address
HTTP
Allow
Protocol: TCP
Port: the port used by the backend server and health check port
100.125.0.0/16
TCP
Allow
Protocol: TCP
Port: health check port
100.125.0.0/16
UDP
Allow
Protocol: UDP and ICMP
Port: health check port
100.125.0.0/16
- Click OK.
Configuring Network ACL Rules
To control traffic in and out of a subnet, you can associate a network ACL with the subnet. Network ACL rules control access to subnets and add an additional layer of defense to your subnets. Default network ACL rules reject all inbound and outbound traffic. If the subnet of a load balancer or associated backend servers has a network ACL 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 network ACL rule to permit access from 100.125.0.0/16.
ELB translates the public IP addresses used to access backend servers into private IP addresses in 100.125.0.0/16. You cannot configure rules to prevent public IP addresses from accessing backend servers.
Network ACL rules configured for the backend subnet of the load balancer will not restrict the traffic from the clients to the load balancer. If these rules are configured, the clients can directly access the load balancer. To control access to the load balancer, configure access control for all listeners added to the load balancer
For details, see Access Control.
- 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 Networking > Virtual Private Cloud.
- In the navigation pane on the left, choose Access Control > Network ACLs.
- In the network ACL list, click the name of the network ACL to switch to the page showing its details.
- On the Inbound Rules or Outbound Rules tab page, click Add Rule to add an inbound or outbound rule.
- Action: Select Allow.
- Protocol: The protocol must be the same as the backend protocol.
- Source: Set it to 100.125.0.0/16.
- Source Port Range: Select a port range.
- Destination: Enter a destination address allowed in this direction. The default value is 0.0.0.0/0, which indicates that traffic from all IP addresses is permitted.
- Destination Port Range: Select a port range.
- (Optional) Description: Describe the network ACL rule.
- Click OK.
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