VPN or Direct Connect allows communications between on-premises data centers and VPCs at Layer 3. However, this may require network reconstruction, long cloud migration period, and service interruptions. For details, see Constraints on Communication at Layer 3.
Enterprise switches allow communications between on-premises data centers and VPCs at Layer 2, helping you dynamically and smoothly migrate workloads to the cloud. For details, see Advantages on Communication at Layer 2.
Constraints on Communication at Layer 3
Figure 1 shows the Layer 3 network between on-premises data centers and VPCs using VPN or Direct Connect. Table 1 describes the pain points.
Figure 1 Layer 3 networking diagram
Table 1 Layer 3 networking description
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Description |
VPN or Direct Connect allows the communication between on-premises data centers and VPCs at Layer 3 through routes. |
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Pain Points |
- The CIDR blocks of the on-premises data center and the VPC that are used for communication cannot overlap.
On-premises workloads communicate with each other using IP addresses instead of domain names. If the CIDR blocks of the on-premises data center and the VPC that are used for communication overlap, the on-premises network needs to be reconstructed before the cloud migration, which prolongs the cloud migration period, interrupts businesses, and increases O&M costs.
- Workloads in a subnet have to be migrated together, and cloud and on-premises workloads in the same subnet cannot communicate with each other.
Dozens of different workloads are deployed on each subnet of the on-premises data center. If workloads are migrated by subnet, business continuity cannot be ensured.
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Advantages on Communication at Layer 2
To handle the pain points of cloud migration at Layer 3, you can use enterprise switches to allow the communication between on-premises data centers and VPCs at Layer 2. For details about the advantages of enterprise switches, see Table 2.
Figure 2 Layer 2 networking diagram
Table 2 Layer 2 networking description
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Description |
Enterprise switches establish a Layer 2 network between on-premises data centers and VPCs based on the Layer 3 network established by VPN or Direct Connect. |
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Advantages |
- The CIDR blocks of the on-premises data center and the VPC that are used for communication can overlap.
An enterprise switch allows the network of the on-premises data center to remain unchanged even if the data center and the VPC have overlapping CIDR blocks.
- Workloads can be migrated to the cloud on a server basis, and cloud and on-premises workloads in the same subnet can communicate with each other.
Workloads can be seamlessly migrated to the cloud to prevent any loss caused by cloud migration.
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