Overview

Central Network

Relying on the cloud backbone network, a central network allows you to easily set up a reliable, intelligent enterprise-grade network and manage global network resources on premises and on the cloud. By setting up a central network, you can enable communication between enterprise routers, as well as between enterprise routers and your on-premises data center, in the same region or different regions.

For details about the regions where central networks are available, see Region Availability.

Application Scenarios

Cross-region communication on the cloud: Enterprise routers in different regions are added to a central network as attachments so that resources in these regions can communicate with each other over one network.
Figure 1 Cross-region communication between enterprise routers
Communication between on-premises data centers and the cloud: Enterprise routers and global DC gateways are added to a central network as attachments. In this way, multiple VPCs on the cloud can communicate with on-premises data centers across regions.
Figure 2 Connectivity between enterprise routers and an on-premises data center
Global network: By flexibly changing the central network policies, you can build a global network more conveniently.

Central Network Quotas

**Table 1** Central network quotas
Quota Type	Quota	How to Increase Quota
Central networks in an account	6	Submit a service ticket.
Policies for a central network	500	Submit a service ticket.
Policy document size (KB)	10	The quota cannot be increased.
Enterprise routers on a central network as attachments in a region	1	The quota cannot be increased. Only one enterprise router can be added to a central network as an attachment in a region.
Global DC gateways on a central network as attachments in a region	3	Submit a service ticket.

Central Network Constraints

To use a central network, the following resources must have been created:
- Enterprise router: used to set up a central network
- Global DC gateway: attached to an enterprise router for allowing on-premises data centers to access the cloud across regions
Policy management
- A central network can only have one policy. If you apply another policy for this central network, the policy that was previously applied will be automatically cancelled.
- In each policy, only one enterprise router can be added for a region. All added enterprise routers can communicate with each other by default.
- A policy that is being applied or cancelled cannot be deleted.
Cross-site connection bandwidth management
- A cross-site connection bandwidth cannot be changed or deleted when it is being created, updated, deleted, frozen, unfrozen, or is recovering.
- The total of cross-site connection bandwidths cannot exceed the global connection bandwidth.
- If a cross-site connection bandwidth is deleted, you will still be billed for the global connection bandwidth.

Configuration Process

Figure 3 shows the process of configuring a central network to manage global network resources.

Figure 3 Central network configuration process

**Table 2** Steps for configuring a central network
No.	Step	Description	Reference
1	Create a central network.	After an enterprise router is created, you can create a central network and add the enterprise router to a policy of the central network. In this way, resources can communicate with each other across regions, and network resources in each region can be managed centrally.	Creating a Central Network
2	(Optional) Add attachments.	Attach global DC gateways to the enterprise routers in a specific region of the central network to enable resources to communicate with each other across regions.	Adding Attachments
3	Assign cross-site connection bandwidth.	After adding enterprise routers or global DC gateways in different regions to the same policy, purchase a global connection bandwidth and assign bandwidth for cross-site connections.	Assigning Cross-Site Connection Bandwidth