Flannel is a simple and stable open source Container Network Interface (CNI) plug-in. Flannel enables pods on different nodes to access a virtual private cloud (VPC) by using custom routes that are provided by the VPC. This topic describes how to use Flannel in a Container Service for Kubernetes(ACK) cluster.
Background information
The Flannel network plug-in ensures that the CIDR block of pods does not overlap with the CIDR block of the VPC. The CIDR block of pods is evenly divided and allocated to the nodes in the cluster. Each pod on a node is assigned an IP address that belongs to the CIDR block of the node. The number of IP addresses that can be assigned to pods depends on the mask of the CIDR block of pods.
Usage notes
The cloud controller manager (CCM) manages the default route table of the VPC in which a cluster that uses Flannel is deployed. We recommend that you do not modify the default route table unless necessary. For more information about the CCM, see CCM.
By default, a cluster that uses Flannel does not support multiple VPC route tables. If the VPC of the cluster has more than one route table, you can refer to Configure multiple route tables for a VPC and configure multiple route tables for the cluster. If you use the NAT Firewall, make sure that you add the system route table of the VPC to the list of route tables after you create the firewall. Otherwise, the scaling of cluster nodes may be affected.
If a route table contains conflicting routes, the CCM automatically deletes the routes.
Procedure
On the Create Cluster page, select Flannel for Network Plug-in. The following table describes the parameters. For more information, see Create an ACK managed cluster and Create an ACK dedicated cluster.
Parameter | Description |
VPC | Select a VPC in which you want to deploy the cluster. |
vSwitch | Select the vSwitches that are used by the nodes in the cluster. |
Number of Pods per Node | The maximum number of pods that can be deployed on each node. |
Pod CIDR Block | The CIDR block of pods in the cluster. For more information, see Correlation between the VPC CIDR block and Kubernetes cluster CIDR block. |
Service CIDR | The CIDR block of Services in the cluster. For more information, see Correlation between the VPC CIDR block and Kubernetes cluster CIDR block. |
VPC limits and quotas
A node in a cluster is mapped to a route entry in a route table. By default, each route table for a VPC can contain up to 200 entries. If the number of nodes in a cluster exceeds 200, apply for a quota increase in the log on to the Quota Center console and submit an application
For more information about the VPC limits and quotas, see VPC quotas.