- Release Notes and Announcements
- CLB Release Notes
- [April 15, 2024] Domain Name Upgrade for Domain Name-based Public Network CLB
- [July 25, 2023] Adding Rate Limits on Shared CLB Instances
- [July 3, 2023] CLB API Authentication Upgrade
- [June 9, 2023] Adjusting the Grace Period for Pay-as-you-go CLB Instances
- [March 6, 2023] Launching Domain Name-Based Public CLBs
- [Feb. 24, 2023] Changing Health Check Source IP to 100.64.0.0/10 IP Range
- [July 8, 2022] Classic CLB Upgrade Prompt
- 【October 20, 2021】Classic CLB End-of-Sale Notice
- 【April 27, 2021】Announcement on the Authentication Upgrade for Certain CLB APIs
- Product Introduction
- Purchase Guide
- Getting Started
- Directions
- CLB Instance
- Directions for Upgrading to Domain Name-Based CLB
- Creating CLB Instances
- Creating an IPv6 CLB Instance
- Creating IPv6 NAT64 CLB Instances
- Creating an Anycast CLB Instance
- Configure CLB Forwarding Domain Name
- Configuring CLB Security Group
- Binding Private Network CLB to EIP
- Enabling or Disabling a CLB Instance
- Cloning CLB Instances
- Exporting CLB Instances
- Upgrade to a LCU-supported instances
- Adjusting Specification of LCU-supported CLBs
- Deleting CLB Instances
- Releasing Idle CLB Instances
- Configuring Deletion Protection
- Adjusting Instance Public Network Configurations
- CLB Listener
- CLB Listener Overview
- Configuring TCP Listener
- Configuring a UDP Listener
- Configuring TCP SSL Listener
- Configuring a QUIC Listener
- Configuring an HTTP Listener
- Configuring HTTPS Listener
- Load Balancing Methods
- Session Persistence
- Layer-7 Redirection Configuration
- Layer-7 Custom Configuration
- Layer-7 Domain Name Forwarding and URL Rules
- Using QUIC Protocol on CLB
- SNI Support for Binding Multiple Certificates to a CLB Instance
- Configuring gRPC Support for Layer-7 Protocols
- Real Server
- Health Check
- Certificate Management
- Log Management
- Monitoring and Alarm
- Cloud Access Management
- Classic CLB
- CLB Instance
- Best Practices
- Enabling Gzip Compression & Testing
- HTTPS Forwarding Configurations
- Obtaining Real Client IPs
- Best Practices for Configuring Load Balancing Monitoring Alerts
- Implementing HA Across Multiple AZs
- Load Balancing Algorithm Selection and Weight Configuration Examples
- Configuring WAF protection for CLB listening domain names
- Ops Guide
- Troubleshooting
- API Documentation
- History
- Introduction
- API Category
- Making API Requests
- Instance APIs
- Listener APIs
- Backend Service APIs
- Target Group APIs
- Redirection APIs
- Other APIs
- ModifyLoadBalancersProject
- InquiryPriceCreateLoadBalancer
- InquiryPriceModifyLoadBalancer
- InquiryPriceRenewLoadBalancer
- DescribeLoadBalancerTraffic
- DescribeTaskStatus
- DescribeClsLogSet
- CreateClsLogSet
- CreateTopic
- CreateLoadBalancerSnatIps
- DeleteLoadBalancerSnatIps
- SetLoadBalancerSecurityGroups
- SetSecurityGroupForLoadbalancers
- ReplaceCertForLoadBalancers
- DescribeLoadBalancerListByCertId
- SetLoadBalancerClsLog
- DescribeQuota
- DescribeResources
- Classic CLB APIs
- Load Balancing APIs
- Data Types
- Error Codes
- CLB API 2017
- FAQs
- Service Level Agreement
- Contact Us
- Glossary
- Release Notes and Announcements
- CLB Release Notes
- [April 15, 2024] Domain Name Upgrade for Domain Name-based Public Network CLB
- [July 25, 2023] Adding Rate Limits on Shared CLB Instances
- [July 3, 2023] CLB API Authentication Upgrade
- [June 9, 2023] Adjusting the Grace Period for Pay-as-you-go CLB Instances
- [March 6, 2023] Launching Domain Name-Based Public CLBs
- [Feb. 24, 2023] Changing Health Check Source IP to 100.64.0.0/10 IP Range
- [July 8, 2022] Classic CLB Upgrade Prompt
- 【October 20, 2021】Classic CLB End-of-Sale Notice
- 【April 27, 2021】Announcement on the Authentication Upgrade for Certain CLB APIs
- Product Introduction
- Purchase Guide
- Getting Started
- Directions
- CLB Instance
- Directions for Upgrading to Domain Name-Based CLB
- Creating CLB Instances
- Creating an IPv6 CLB Instance
- Creating IPv6 NAT64 CLB Instances
- Creating an Anycast CLB Instance
- Configure CLB Forwarding Domain Name
- Configuring CLB Security Group
- Binding Private Network CLB to EIP
- Enabling or Disabling a CLB Instance
- Cloning CLB Instances
- Exporting CLB Instances
- Upgrade to a LCU-supported instances
- Adjusting Specification of LCU-supported CLBs
- Deleting CLB Instances
- Releasing Idle CLB Instances
- Configuring Deletion Protection
- Adjusting Instance Public Network Configurations
- CLB Listener
- CLB Listener Overview
- Configuring TCP Listener
- Configuring a UDP Listener
- Configuring TCP SSL Listener
- Configuring a QUIC Listener
- Configuring an HTTP Listener
- Configuring HTTPS Listener
- Load Balancing Methods
- Session Persistence
- Layer-7 Redirection Configuration
- Layer-7 Custom Configuration
- Layer-7 Domain Name Forwarding and URL Rules
- Using QUIC Protocol on CLB
- SNI Support for Binding Multiple Certificates to a CLB Instance
- Configuring gRPC Support for Layer-7 Protocols
- Real Server
- Health Check
- Certificate Management
- Log Management
- Monitoring and Alarm
- Cloud Access Management
- Classic CLB
- CLB Instance
- Best Practices
- Enabling Gzip Compression & Testing
- HTTPS Forwarding Configurations
- Obtaining Real Client IPs
- Best Practices for Configuring Load Balancing Monitoring Alerts
- Implementing HA Across Multiple AZs
- Load Balancing Algorithm Selection and Weight Configuration Examples
- Configuring WAF protection for CLB listening domain names
- Ops Guide
- Troubleshooting
- API Documentation
- History
- Introduction
- API Category
- Making API Requests
- Instance APIs
- Listener APIs
- Backend Service APIs
- Target Group APIs
- Redirection APIs
- Other APIs
- ModifyLoadBalancersProject
- InquiryPriceCreateLoadBalancer
- InquiryPriceModifyLoadBalancer
- InquiryPriceRenewLoadBalancer
- DescribeLoadBalancerTraffic
- DescribeTaskStatus
- DescribeClsLogSet
- CreateClsLogSet
- CreateTopic
- CreateLoadBalancerSnatIps
- DeleteLoadBalancerSnatIps
- SetLoadBalancerSecurityGroups
- SetSecurityGroupForLoadbalancers
- ReplaceCertForLoadBalancers
- DescribeLoadBalancerListByCertId
- SetLoadBalancerClsLog
- DescribeQuota
- DescribeResources
- Classic CLB APIs
- Load Balancing APIs
- Data Types
- Error Codes
- CLB API 2017
- FAQs
- Service Level Agreement
- Contact Us
- Glossary
Error Description
In a CLB UDP health check, the health check result is different from the actual status of the real server port.
Cause
In a UDP health check, the CLB instance sends a UDP probe message to the real server. If the PING command is successful and an error message
port XX unreachable is not returned within the response timeout period, the real server is considered healthy. Otherwise, the real server is considered unhealthy.There are two possible causes for this error:
The response timeout period is too short for the real server to return a ICMP message
reply or port unreachable to the health check nodes, leading to an inaccurate health check result.The real server restricts the rate at which ICMP messages are generated. In this case, when a service exception occurs,
port XX unreachable cannot be returned, and the CLB instance considers that the health check is successful as no ICMP response is received. Therefore, the health check result is inconsistent with the actual server health.Troubleshooting Procedure
1. Check whether the response timeout period is too short. Log in to the CLB Console, and increase the timeout duration for the UDP listener. For more details, see Configuring a UDP Listener.
Note:
UDP health checks are different from other health checks. If the health check timeout period is too short, the health check result will switch back and forth between healthy and unhealthy.
2. If the error persists, check whether the real server restricts the frequency of ICMP messages. Log in to the real server, and run the following commands to check the rate limit.
sysctl -q net.ipv4.icmp_ratelimitsysctl -q net.ipv4.icmp_ratemask
3. Check whether the return value of the first command is
0 or 1000 (default). We commend using the default value.4. If the error persists, run the following command to disable the rate limit of the ICMP
port unreachable messages.Note:
Note that if the rate limit of ICMP
port unreachable messages is lifted, when the real server is connected to the public network and encounters UDP port scanning attack, it will keep returning port unreachable messages# Run the command `net.ipv4.icmp_ratemask` in step 2 to query the rate mask.# Keep the first three digits of the returned rate mask unchanged, and subtract 8 from the last digit. For example, if the mask returned is “6168”, replace "xxxx" with 6160; if it is 1819, replace "xxxx" with 1811.sysctl -w net.ipv4.icmp_ratemask=xxxx
Yes
No
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