All Products
Search
Document Center

Troubleshooting for testing ECS instance disconnection by using ping command

Last Updated: Dec 31, 2020

Introduction

This article describes how to troubleshoot the test of ECS instance disconnection by using the command for ping failure.

Background

The ECS instance cannot be pinged. Possible causes are as follows:

  1. Check the status of the ECS instance. Only when the ECS instance is in running status can it provide external access to services. The inspection steps are as follows:

    1. Log on to the ECS console.
    2. Click instances in the left-side navigation pane to view the status of the instance.
      • The target instance is not in the running state. See ECS instance lifecycle to determine the solution based on the instance state.
      • The target instance is in the running state. See the next step to continue.
  2. Check whether you can connect to the machine through remote connection.
    • If you can connect to the server remotely, but the ping fails, see the following operations to check whether ICMP has been added.
      1. Log on to the ECS console.
      2. In the left-side navigation pane, click instance image > Instance.
      3. In the top navigation bar, select a region.
      4. In instance list page in the ECS instance, and then click the instance ID to enter the instance details page.
      5. In the left-side navigation pane, click security groups, and click the security group ID to go to the security group rules page.
      6. On the security group rules page, click inbound and check whether ICMP has been added. If the action is not performed, add security group rules. For more information, see add security group rules.
        • If the ping fails, check whether the firewall of the machine is blocked. If the network services are normal but the ping fails, it is generally because the firewall has restricted the specific port and protocol.
          • Windows: For more information, see configure a firewall for remote connection to a Windows instance.
          • Linux: for CentOS, see how to configure the default Firewall for an ECS instance running CentOS 7.
        • If the external network cannot ping and access the server port, but the access from the server to the external network is normal, check whether the Cloud Firewall is used. If a firewall is used, log on to the Cloud Firewall console. On the access control page, check whether inbound denial rules do not allow access to the port and ICMP protocol.
    • If you cannot connect to the server remotely, log on to the server through VNC, and check whether the server can start properly.
      Note:
      • The server cannot be started. For example, Windows already has a blue screen. If your server has a blue screen, submit a ticket to Alibaba Cloud technical support personnel for further troubleshooting.
      • The machine can start normally. Please log in and check whether the network interface controller service in the machine is normal.
  3. During the black hole period, you cannot access the server through public networks. For more information, see Alibaba Cloud black hole policies.
  4. Check whether the client environment cannot be pinged. After switching to another client environment, the server can run normally if only a certain client environment is disconnected. In this case, we recommend that you perform two-way MTR on the client and server, and submit a ticket to contact Alibaba Cloud technical support personnel for further troubleshooting. For more information about how to test the link, see the using ping command when packet loss or disconnection method .
  5. Check whether the hostname is in China (Hong Kong) or China (overseas). When machines from mainland China visit Hong Kong or overseas machines, the link quality may be affected by the carriers' lines. We recommend that you try again in a short period of time.
  6. Check whether security center sends you any suspicious alerts. A victim may be compromised. You can install third-party security software to detect viruses.

Documentation

Application scope

  • ECS