如何解决k8s CNI 子网不够问题

猿柒

9天前发布

问题现象

CNI 状态 CrashLookBackOff

问题原因

默认环境下 k8s 每个 node 的CNI subnet 子网是一个 24位掩码的子网。当集群总结点数超过 255 个将导致 CNI 子网不足。我们有两种方式结局

解决方案

init 集群指定 kube-controller-manager 参数

apiVersion: kubeadm.k8s.io/v1beta3
kind: InitConfiguration
bootstrapTokens:
- groups:
  - system:bootstrappers:kubeadm:default-node-token
  token: abcdef.0123456789abcdef
  ttl: 24h0m0s
  usages:
  - signing
  - authentication
localAPIEndpoint:
  advertiseAddress: 192.168.10.11
  bindPort: 6443
nodeRegistration:
  criSocket: /var/run/dockershim.sock
  imagePullPolicy: IfNotPresent
  taints: null
---
apiVersion: kubeadm.k8s.io/v1beta3
kind: ClusterConfiguration
apiServer:
  certSANs:
    - master1
    - 192.168.10.11
  timeoutForControlPlane: 4m0s
certificatesDir: /etc/kubernetes/pki
clusterName: kubernetes
controlPlaneEndpoint: 192.168.10.10:6443
controllerManager: {}
dns: {}
etcd:
  local:
    dataDir: /var/lib/etcd
controllerManager:
  extraArgs: # 这里指定每个节点使用 26 位掩码
    "node-cidr-mask-size": "26"
imageRepository: registry.cn-hangzhou.aliyuncs.com/google_containers
kubernetesVersion: 1.23.0
networking:
  podSubnet: 172.244.0.0/16
  serviceSubnet: 172.66.0.0/12
  nodeCidrMaskSize: 26
scheduler: {}
---
kind: KubeletConfiguration
apiVersion: kubelet.config.k8s.io/v1beta1
cgroupDriver: cgroupfs
~

针对已建成集群，需要解决这个问题

修改 /etc/kubernetes/manifests/kube-controller-manager.yaml 中 spec.containers.[0].command 中的参数

....
spec:
  containers:
  - command:
    - kube-controller-manager
    - --allocate-node-cidrs=true
    - --authentication-kubeconfig=/etc/kubernetes/controller-manager.conf
    - --authorization-kubeconfig=/etc/kubernetes/controller-manager.conf
    - --bind-address=127.0.0.1
    - --client-ca-file=/etc/kubernetes/pki/ca.crt
    - --cluster-cidr=172.244.0.0/16
    - --cluster-name=kubernetes
    - --cluster-signing-cert-file=/etc/kubernetes/pki/ca.crt
    - --cluster-signing-key-file=/etc/kubernetes/pki/ca.key
    - --controllers=*,bootstrapsigner,tokencleaner
    - --kubeconfig=/etc/kubernetes/controller-manager.conf
    - --leader-elect=true
    - --node-cidr-mask-size=26 # 添加启动参数
    - --requestheader-client-ca-file=/etc/kubernetes/pki/front-proxy-ca.crt
    - --root-ca-file=/etc/kubernetes/pki/ca.crt
    - --service-account-private-key-file=/etc/kubernetes/pki/sa.key
    - --service-cluster-ip-range=172.66.0.0/12
    - --use-service-account-credentials=true
    image: registry.cn-hangzhou.aliyuncs.com/google_containers/kube-controller-manager:v1.23.0
...

重启 master 节点 kube-controller-manager

对于已经加入集群节点，只需要重新加入集群节点掩码就会变成 26 位

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