Note: In this document, a classic ECS refers to an ECS instance created in the classic network, while a VPC ECS refers to an ECS instance created in the VPC network.
Virtual Private Cloud (VPC) a private network dedicated to you in Alibaba Cloud. You can use Alibaba Cloud resources and products in your own VPC. The VPC network has the following advantages:
Secure and isolated network environment
Based on tunneling technology, VPC isolates the data link layer and provides an independent, isolated, and safe network for each user. Different VPCs are completely isolated from each other. Resources within a VPC can communicate with each other over the intranet, but cannot directly communicate with resources in other VPCs unless you have configured a public IP or a VPN gateway.
Controllable network configurations
You have full control over your own VPC network. You can select its IP address range, create subnets, and configure route tables. Additionally, you can connect a VPC to your local IDC network to form an on-demand network environment, which allows you to smoothly migrate applications to Alibaba Cloud and expand the network topology of the local IDC.
You can use the hybrid addition and access solution to smoothly migrate your system to the VPC network. With the ClassicLink function, the classic ECS instances can access the resources in the VPC network during the migration, which guarantees the service continuity.
Hybrid addition and access migration
If your system depends on RDS, SLB, or other cloud products, we recommend that you use this solution. It is a seamless migration solution, allowing you to migrate your system to the VPC network without interrupting your services.
During the migration, you can use the ClassicLink function to connect an ECS instance in the classic network to the VPC network. Therefore, the ECS instances that have not been migrated to the VPC network can still access the cloud resources created in the VPC network.
Single ECS migration
If your system only depends on ECS, and ECS restart has no effect on your system, we recommend that you use this solution.
The hybrid access and hybrid addition solution is a seamless migration solution. Firstly, you have to create the required cloud resources (such as ECS) in the VPC network to be migrated to, and then use this solution to smoothly migrate your system to the VPC. After all the systems have been migrated to VPC, release the cloud resources in classic network to complete the whole migration process. For more information, see Hybrid addition and acess migration.
Cloud products like RDS and OSS support hybrid access, that is, they can be accessed by an ECS instance in the VPC network and an ECS instance in the VPC network at the same time. In general, these products have two endpoints, one is used for the classic network access and the other one is used for the VPC network access.
Hybrid addition is that you can add both the classic ECS instances and VPC ECS instances to a Server Load Balancer (SLB) instance. The VServer group also supports hybrid addition.
Note: For the Layer-4 Server Load Balancer that is created in the VPC network, if you add both the classic ECS instances and VPC ECS instances to an SLB instance of the VPC network, you cannot obtain the client's real IP address on the classic ECS instance, but can obtain it on the VPC ECS instance. Hybrid access has no effect on the Layer-7 Server Load Balancer.
Note the following when using this solution:
This solution meets most of the system migration requirements. If the ECS instances in the classic network has to communicate with the cloud resources in the VPC network, use the ClassicLink function together.
This solution can only be used to migrate a system from the classic network to the VPC network.