Why Can't an EIP Be Pinged?

Symptom

After you purchase an EIP and bind it to an ECS, the EIP cannot be pinged on a local server or other cloud servers.

Fault Locating

The following fault causes are sequenced based on their occurrence probability.

If the fault persists after you have ruled out a cause, check other causes.

Checking Security Group Rules

ICMP is used for the ping command. Check whether the security group accommodating the ECS allows ICMP traffic.

1. Log in to the management console.
2. Click in the upper left corner and select your region and project.
3. Under Compute, click Elastic Cloud Server.
4. On the Elastic Cloud Server page, click the name of the target ECS.

   The page providing details about the ECS is displayed.

5. Click the Security Groups tab, expand the information of the security group, and view security group rules.
6. Click the security group ID.

   The system automatically switches to the Security Group page.

7. On the Outbound Rules page, click Add Rule. In the displayed dialog box, set required parameters to add an outbound rule.

   Table 2 Security group rules

   Transfer Direction	Type	Protocol/Port Range	Source
   Outbound	IPv4	ICMP/Any	0.0.0.0/0 0.0.0.0/0 indicates all IP addresses.

8. On the Inbound Rules tab, click Add Rule. In the displayed dialog box, set required parameters to add an inbound rule.

   Table 3 Security group rules

   Transfer Direction	Type	Protocol/Port Range	Source
   Inbound	IPv4	ICMP/Any	0.0.0.0/0 0.0.0.0/0 indicates all IP addresses.

9. Click OK to complete the security rule configuration.

Checking Firewall Settings

If a firewall is enabled on the ECS, check whether the firewall blocks the ping operations.

Checking Whether Ping Operations Have Been Disabled on the ECS

Linux

Checking ACL Rules

By default, no ACL is configured for a VPC. If a network ACL is associated with a VPC, check the ACL rules.

1. Check whether the subnet of the ECS has been associated with a network ACL.

   If an ACL name is displayed, the network ACL has been associated with the ECS.

2. Click the ACL name to view its status.
3. If the network ACL is enabled, add an ICMP rule to allow traffic.
   

   The default network ACL rule denies all incoming and outgoing packets. If a network ACL is disabled, the default rule is still effective.

Checking Whether the Network Is Functional

1. Use another ECS in the same region to check whether the local network is functional.

   Use another ECS in the same region to ping the affected EIP. If the EIP can be pinged, the VPC is functional. In such a case, rectify the local network fault and ping the affected EIP again.

2. Check whether the link is accessible.

   A ping failure is caused by packet loss or long delay, which may be caused by link congestion, link node faults, or heavy load on the ECS.

Checking the ECS Route Configuration If Multiple NICs Are Used

Generally, the default route of an OS will preferentially select the primary NIC. If an extension NIC is selected in a route and the network malfunctions, this issue is typically caused by incorrect route configuration.

• If the ECS has multiple NICs, check whether the default route is available.
  1. Log in to the ECS and run the following command to check whether the default route is available:

     ip route

     Figure 2 Default route
     
  2. If the route is unavailable, run the following command to add it:

     ip route add default via XXXX dev eth0

     

     In the preceding command, XXXX specifies a gateway IP address.

Checking Domain Name Resolution If the Domain Name Cannot Be Pinged

If you can ping the EIP but not the domain name, the possible cause is that an error occurred in domain name resolution.

1. Check the domain name resolution.

   If the domain name records are incorrectly configured, the domain name may fail to be resolved.

   Switch to the DNS management console to view details about the domain name resolution.

2. Check the DNS server configuration.