Why Is My ECS Unable to Communicate at a Layer 2 or Layer 3 Network?

Symptom

An ECS cannot ping the gateway of the subnet where the ECS resides.

Troubleshooting

Locate the fault based on the following procedure.

Figure 1 Troubleshooting procedure

1. Checking Whether the ECS Has Obtained an IP Address
2. Checking Whether the Security Group Allows Communication Between Subnets Involved in the VPC Peering Connection
3. Checking Whether the Network ACL Allows Communication Between Subnets Involved in the VPC Peering Connection

Checking Whether the ECS Has Obtained an IP Address

Log in to the ECS, and run ifconfig or ip address to check the ECS NIC IP address. If an ECS runs Windows, use ipconfig.

If the ECS does not have an IP address, check whether DHCP has been enabled for the required subnet.

Switch to the subnet details page and check whether the DHCP function has been enabled.

For details, see Why Does My ECS Fail to Obtain an IP Address?

Checking Whether the Security Group Allows Communication Between Subnets Involved in the VPC Peering Connection

You can view the security group on the ECS details page. Check whether a security group rule has been configured to allow the ECS to communicate with the peer VPC subnet.

Figure 2 Security group rule

Checking Whether the Network ACL Allows Communication Between Subnets Involved in the VPC Peering Connection

In the navigation pane on the left of the VPC console, choose Network ACLs. On the displayed page, select the network ACL associated with the subnets of the VPC peering connection. On the network ACL details page, check whether network ACL rules allow communication between the subnets involved in the VPC peering connection.

Figure 3 Network ACL rule