Configuring the Multi-Cluster Networking

Before creating an MCS object, ensure connectivity of both inter-cluster nodes and containers.

Check the connectivity by referring to Table 1. If the network between nodes or containers is not connected, connect them. If they still cannot be connected, rectify the fault by referring to FAQ.

**Table 1** Connectivity of both inter-cluster nodes and containers
Inter-Cluster Network	How to Check	How to Connect
Node connectivity	Ping the IP address of a node in cluster B from cluster A. If the ping succeeds, the node connectivity is normal.	Configure the network type. Set the network type to underlay for inter-cluster pod communication. For details, see Cluster Network Types. Connect the network between clusters. Network connectivity between CCE clusters: CCE clusters in the same VPC can communicate with each other by default. Use a VPC peering connection to connect CCE clusters across VPCs. Network connectivity between on-premises clusters: Set Cilium to the underlay mode and enable BGP for Cilium. For details, see Cilium. Network connectivity between clusters of other types: Enable the network between clusters of other types as required.
Container connectivity	Use cURL to access a pod in cluster B from cluster A. If the access succeeds, the container connectivity is normal.

Cluster Network Types

Ensure that underlay networks are supported for inter-cluster pod communication. The following table lists the types of clusters that support underlay networks.

**Table 2** Types of clusters that support underlay networks
Cluster Type	Cluster Subtype	Network Type	Support Underlay Network
Huawei Cloud clusters	CCE clusters	Container tunnel network	No
	CCE clusters	VPC network	Yes
	CCE Turbo clusters	Cloud native network 2.0	Yes
On-premises clusters	On-premises clusters	Overlay and underlay networks The overlay network is used by default. You need to manually enable the underlay network. For details about the underlay network, see Cilium.	Yes
Multi-cloud clusters	Multi-cloud clusters	Overlay and underlay networks The overlay network is used by default. You need to manually enable the underlay network. For details about the underlay network, see Cilium.	Yes
Attached clusters	Attached clusters	Unknown	Network type–based

FAQ

If nodes or containers in different clusters cannot access each other, check the items listed in the following table.

**Table 3**
Check Item	Fault Locating	Solution
Whether the cluster version is v1.21 or later	Access the cluster details page.	Upgrade the cluster. For details, see Upgrading a Cluster.
Whether clusters can be accessed over an underlay network	Check this item by referring to Table 2.	Configure the network type by referring to Table 2.
Whether CIDR blocks overlap in the routes of the VPC peering connection	Go to the VPC peering connection details page.	Modify the overlapped CIDR blocks.