Problem
When you use a Windows instance, the configurations of the Elastic Network Interface (ENI) in the operating system become invalid. For example, issues including network connections are interrupted, connections fail to be established, IP addresses become invalid, subnet configurations (subnet mask and default network) become invalid, traffic routing has exceptions, and VLAN configurations become invalid may occur.
ENI configurations may become invalid in the following scenarios:
After an ECS instance to which multiple disks are attached is created, hot swapping is alternately performed to the disks and ENIs and the ECS instance is restarted.
After an ECS instance to which a secondary ENI is associated is created, hot swapping is alternately performed to the disks and ENIs and the ECS instance is restarted.
For example, create a Windows instance to which three disks are attached, then detach the disks from the instance. Associate a new ENI to the instance and configure a secondary private IP address.
Restart the ECS instance. The ENI configurations become invalid.
Cause
The Windows operating system names the ENIs according to the sequence in which the ENIs are identified. However, when hot swapping is alternately performed to the disks and ENIs, the identification sequence of the devices is affected. As a result, the device numbers change. In this case, the network configurations of ENIs cannot be applied to the new devices, and the network configurations become invalid.
Solutions
Use one of the following methods to resolve this issue depending on whether secondary private IP or IPv6 addresses are assigned to the ENI.
No secondary private IP or IPv6 addresses are assigned to the ENI
If no secondary private IP or IPv6 addresses are assigned to the ENI, configure the network adapter in the Windows system to automatically obtain an IP address. Perform the following steps:
Connect to the instance.
For more information, see Connect to a Windows instance by using a password.
Open Network and Sharing Center.
Click Change adapter settings.
Double-click the network connection in use. For example, double-click Ethernet. Click Properties in the Ethernet Status dialog box.
In the Ethernet Properties dialog box, double-click Internet Protocol Version 4 (TCP/IPv4).
In the Internet Protocol Version 4 (TCP/IPv4) Properties dialog box, select Obtain an IP address automatically and Obtain DNS server address automatically. Click OK.
Secondary private IP or IPv6 addresses are assigned to the ENI
If secondary private IP or IPv6 addresses are assigned to the ENI, reconfigure the IP address after you restart the instance. Perform the following steps:
Configure secondary private IPv4 addresses.
For more information, see Assign secondary private IP addresses.
Configure secondary private IPv6 addresses.
For more information, see Configure an IPv6 address for an ECS instance.
The ENI network configurations become valid after you configure secondary private IP addresses.