The IP address of pod can be fixed, and kubernetes dynamic IP network allocation management plug-in based on etcd distributed storage is used.kube-ipam allocates ip addresses out of a set of address ranges.It stores the state locally on the remote etcd, therefore ensuring uniqueness of IP addresses in a cluster.Optionally, it can include a DNS configuration from a resolv.conf file on the host.

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[1] Introduction

Some scenarios often rely on IP addresses and need to use Pods with fixed IP addresses. You can use kube-ipam to easily solve this type of problem. For example, in the mysql master-slave architecture, the synchronization between the master database and the slave database; for example, when keepalived is doing cluster HA, the communication between the two nodes is detected; for example, some security protection equipment needs to be based on IP addresses for network security Scenarios restricted by access policies, etc.

Kube-ipam implements kubernetes dynamic IP network allocation management based on etcd distributed storage, ensuring that Pods in the kubernetes cluster have fixed IP addresses. After using the kube-ipam configuration, the fixed-ip Pod in the above figure can still keep the original IP address fixed after being destroyed and rebuilt.

[2] Install kube-ipam

Enable and configure CNI directory

Please make sure that your kubelet takes the three correct parameters network-plugin, cni-conf-dir and cni-bin-dir. An example configuration of kubelet is given below:

# cat /etc/systemd/system/kubelet.service 
...
ExecStart=/usr/local/bin/kubelet \
...
  --network-plugin=cni \
  --cni-conf-dir=/etc/cni/net.d \
  --cni-bin-dir=/opt/cni/bin/ \
...

Get and install kube-ipam

kube-ipam binary program files can be obtained by download or compile, and copy the kube-ipam binary to the /opt/cni/bin/ directory

# wget https://github.com/cloudnativer/kube-ipam/releases/download/v0.2.0/kube-ipam-v0.2.0-x86.tgz
# tar -zxvf kube-ipam-v0.2.0-x86.tgz
# mv kube-ipam-v0.2.0-x86/kube-ipam /opt/cni/bin/kube-ipam

[3] /etc/cni/net.d network configuration

3.1 Configure IP subnet and etcd storage

The IP subnet information of pod is set by subnet parameter, and the gateway of pod is set by gateway parameter.You can configure the etcd address and certificate to be stored in kubernetes pod IP address in etcdConfig parameter.

Edit /etc/cni/net.d/1-kube-ipam.conf files on all kubernetes node servers.

# cat /etc/cni/net.d/1-kube-ipam.conf
{
        "cniVersion":"0.3.1",
        "name": "k8snetwork",
        "type": "macvlan",
        "master": "eth0",
        "ipam": {
                "name": "kube-subnet",
                "type": "kube-ipam",
                "etcdConfig": {
                        "etcdURL": "https://192.168.1.50:2379,https://192.168.1.58:2379,https://192.168.1.63:2379",
			"kubeConfig": "/etc/kubernetes/pki/kubectl.kubeconfig"
                        "etcdCertFile": "/etc/kubernetes/ssl/etcd.pem",
                        "etcdKeyFile": "/etc/kubernetes/ssl/etcd-key.pem",
                        "etcdTrustedCAFileFile": "/etc/kubernetes/ssl/ca.pem"
                },
                "subnet": "10.188.0.0/16",
                "fixedStart": "10.188.0.10",
                "fixedEnd": "10.188.0.255",
                "rangeStart": "10.188.1.0",
                "rangeEnd": "10.188.255.254",
                "gateway": "10.188.0.1",
                "routes": [{
                        "dst": "0.0.0.0/0"
                }],
                "resolvConf": "/etc/resolv.conf"
        }
}

3.2 Configuration parameter description

• type (string, required): fill in your CNI plug-in type, such as macvlan, ipvlan, kube-router, bridge, calico, etc.(it can also be combined with 'Multus' to support more CNI plug-ins)
• routes (string, optional): list of routes to add to the container namespace. Each route is a dictionary with "dst" and optional "gw" fields. If "gw" is omitted, value of "gateway" will be used.
• resolvConf (string, optional): Path to a resolv.conf on the host to parse and return as the DNS configuration
• etcdConfig, an object of etcd address info
  • etcdURL (string, required): The URL of etcd
  • etcdCertFile (string, required): The cert file of etcd
  • etcdKeyFile (string, required): The key file of etcd
  • etcdTrustedCAFileFile (string, required): The ca file of etcd
  • kubeConfig (string, required): The kubeconfig file of kubernetes
• ranges, (array, required, nonempty) an array of arrays of range objects:
  • subnet (string, required): CIDR block to allocate out of.
  • rangeStart (string, optional): IP inside of "subnet" from which to start allocating addresses. Defaults to ".2" IP inside of the "subnet" block.
  • rangeEnd (string, optional): IP inside of "subnet" with which to end allocating addresses. Defaults to ".254" IP inside of the "subnet" block for ipv4, ".255" for IPv6
  • gateway (string, optional): IP inside of "subnet" to designate as the gateway. Defaults to ".1" IP inside of the "subnet" block.

Tip: ranges can support the configuration format of multiple subnets. See multiple-subnets documentation for details.

[4] Kubernetes fixed pod IP address

4.1 Fixed pod IP configuration

The fixed allocation of pod IP address can be realized by configuring kube-ipam.ip, kube-ipam.netmask and kube-ipam.gateway parameters in annotations.
In /etc/cni/net.d/1-kube-ipam.conf,The range of the pod IP address is set in rangestart and rangeend.But if you need to keep the pod IP address fixed, please do not set the value of kube-ipam.ip within this range.
Edit fixed-ip-test-Deployment.yaml , which is used to create a fixed IP pod:

# cat fixed-ip-test-Deployment.yaml
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: fixed-ip-test
  namespace: default
  labels:
    k8s-app: cloudnativer-test
spec:
  replicas: 1
  strategy:
    type: RollingUpdate
    rollingUpdate:
      maxUnavailable: 1
  selector:
    matchLabels:
      k8s-app: cloudnativer-test
  template:
    metadata:
      labels:
        k8s-app: cloudnativer-test
      annotations:
        kube-ipam.ip: "10.188.0.216"
        kube-ipam.netmask: "255.255.0.0"
        kube-ipam.gateway: "10.188.0.1"
    spec:
      containers:
      - name: fixed-ip-test
        image: nginx:1.7.9
        imagePullPolicy: IfNotPresent
        ports:
        - name: http
          containerPort: 80  
---

Kube-ipam only supports the fixed IPv4 address, and we will provide the fixed IPv6 address function in the future.
Notice: If you want to create a Pod with random IP, you only need to remove the kube-ipam.ip, kube-ipam.netmask and kube-ipam.gateway configuration of annotations.

4.2 Create a fixed IP pod

Use the kubectl apply command to create a fixed IP pod:

# kubectl apply -f fixed-ip-test-Deployment.yaml
#
# kubectl get pod -o wide
  NAME                             READY   STATUS    RESTARTS   AGE     IP             NODE   
  fixed-ip-test-6d9b74fd4d-dbbsd   1/1     Running   0          2d23h   10.188.0.216   192.168.20.21

At this point, the fixed-ip-test-6d9b74fd4d-dbbsd is fixed to 10.188.0.216.

4.3 After rescheduling, the pod IP remains unchanged

Use the kubectl delete command to delete this pod, and kuberntes will automatically start a new fixed IP test pod:

# kubectl delete pod fixed-ip-test-6d9b74fd4d-dbbsd
#
# kubectl get pod -o wide
  NAME                             READY   STATUS    RESTARTS   AGE   IP             NODE   
  fixed-ip-test-6d9b74fd4d-xjhek   1/1     Running   0          1h    10.188.0.216   192.168.30.35

At this time, the IP address of the newly started fixed-ip-test-6d9b74fd4d-xjhek is still 10.188.0.216.

Here is another example of using kube-ipam fixed pod IP in calico CNI environment, please click here to view it!

[5] View logs

Check /var/log/kube-ipam.log file on kubernetes node to get the system log information of kube-ipam.

[6] Layered network security architecture

kube-ipam can be combined with multus for networking, which can support more fixed container IP addresses in the CNI plug-in scenario.For example, we can implement web and database layered network security access architecture based on kube-ipam and multus, so that a pod can support multiple network interfaces such as random IP and fixed IP at the same time. This deployment method is conducive to the security personnel to isolate multiple network areas such as application network and database, and effectively control the container cluster network architecture.

The figure above shows that each Pod has 2 interfaces: eth0 and net1. Eth0 serves as the network interface for external users to access the web pod; and net1 is an additional container network card that serves as the internal network communication from the web Pod to the database Pod.

[7] How to Contribute

If you have problems in use, you can click here submit issues to us, or fork it and submit PR.

# git clone your-fork-code
# git checkout -b your-new-branch
# git commit -am "Fix bug or add some feature"
# git push origin your-new-branch