Alibaba Cloud DNS:Ping health check

Parameter settings

1. Template Name: The name of the health check template. For easy identification, use a name that indicates the health check protocol.

2. Type: The IP address type of the probe nodes. Valid values are IPv4 and IPv6.

3. Protocol: Select Ping to monitor metrics for the target IP address, such as network reachability, packet loss rate, and latency.

4. ICMP Packages Sent

   The number of ICMP packets to send for each ping health check. This value is used to calculate the packet loss rate and is fixed at 20.

5. Packet Loss Rate

   The packet loss rate is calculated for the ICMP packets sent during each ping health check. The formula is: Packet loss rate = (Lost packets / Total ICMP packets sent) × 100%. An alarm is triggered if the packet loss rate reaches this threshold. Valid values: 10%, 30%, 80%, 90%, and 100%.

6. Interval

   The interval between ping health checks. The default interval is 1 minute. The minimum interval is 15 seconds, which is available only for Ultimate Edition instances.

7. Timeout Period

   For each ping health check, the system calculates the response time for the sent ICMP packets. If a packet does not return within the specified timeout period, the health check is considered to have timed out. Valid values: 2 seconds, 3 seconds, 5 seconds, and 10 seconds.

8. Retries

   The number of consecutive failed health checks that must occur before the application service is considered abnormal. This setting helps prevent false alarms caused by transient network jitter. Valid values: 1, 2, and 3.

   • 1: The application service is considered abnormal after one failed health check.

   • 2: The application service is considered abnormal after two consecutive failed health checks.

   • 3: The application service is considered abnormal after three consecutive failed health checks.

     Important

     If the target address is disconnected from the network or returns an `ICMP destination unreachable` message, the health check is not considered a failure and no alarm is triggered. You must resolve the network issue for the address or switch to an HTTP health check task.

7. Detection Node

   The geographic locations of the nodes that perform ping health checks. The system provides the following default probe nodes:

   Node type	Geographic location
   BGP Nodes	Qingdao, Zhangjiakou, Beijing, Hohhot, Shenzhen, Shanghai, Hangzhou
   Overseas Nodes	Malaysia, Germany, China (Hong Kong), Singapore, California, Japan
   ISP Nodes	Changsha Telecom, Xi'an Telecom, Nanjing Unicom, Zhengzhou Telecom, Tianjin Unicom, Nanjing Mobile, Dalian Unicom, Shenzhen Mobile, Dalian Mobile, Qingdao Telecom

   Important

   • If all addresses in the address pool are Alibaba Cloud addresses and you use a blackhole filtering policy for fault testing, select carrier nodes as the probe nodes. This is because blackhole filtering is an access control list (ACL) policy that takes effect on the Internet traffic between the Alibaba Cloud network and carrier networks. Traffic between Alibaba Cloud IP addresses flows mostly within the Alibaba Cloud network, which reduces the effectiveness of the probes.

   • Difference between BGP nodes and carrier nodes: Border Gateway Protocol (BGP) nodes automatically select the optimal carrier network. For example, if you use a BGP node in Shanghai and the China Mobile line fails, the probe node may switch to the China Telecom line. The probe node switches to an available line unless all lines fail. In contrast, a carrier node uses only its specified carrier network and does not have this optimization mechanism.

   • To configure a whitelist for access sources on your server, click View Monitoring Node IP Addresses to obtain the IP addresses of the probe nodes.

   • If the IP address to be probed is located outside China, select international nodes.

8. Detected Node Failure Rate

   The percentage of selected probe nodes that must report a health check as failed before the application service is considered abnormal. Valid values: 20%, 50%, 80%, and 100%.

Configuration

Create a probe template

1. Go to the Alibaba Cloud DNS - Global Traffic Manager console.

2. On the Health Check Template tab, click Create Health Check Template. In the dialog box that appears, configure the parameters and submit the form.