When creating an ECS instance in your Alibaba Cloud VPC, you must specify a VSwitch for that instance at the same time. Otherwise, you will not be able to create this ECS instance. This is true according to the Alibaba Cloud documentation on ECS1. A VSwitch is a basic network device of a VPC and is used to connect different cloud product instances deployed in a VPC2. A VSwitch defines a network segment within a VPC and allows you to specify the IP address range, network mask, and gateway for the network segment2. When you create an ECS instance, you must select a VSwitch that belongs to the same zone as the ECS instance3. If you do not specify a VSwitch, the ECS instance will not be able to communicate with other cloud product instances in the VPC or access the Internet. References: 1: Create an instance by using the provided wizard - Elastic Compute Service - Alibaba Cloud Documentation Center 2: What is a VSwitch? - Virtual Private Cloud - Alibaba Cloud Documentation Center 3: Create an instance by using the advanced wizard - Elastic Compute Service - Alibaba Cloud Documentation Center : [VPC FAQ - Virtual Private Cloud - Alibaba Cloud Documentation Center]