Managed DHCP

Managed DHCP

Available as of v1.3.0

Beginning with v1.3.0, you can configure IP pool information and serve IP addresses to VMs running on Harvester clusters using the embedded Managed DHCP feature. This feature, which is an alternative to the standalone DHCP server, leverages the vm-dhcp-controller add-on to simplify guest cluster deployment.

note

Harvester uses the planned infrastructure network so you must ensure that network connectivity is available and plan the IP pools in advance.

Install and Enable the vm-dhcp-controller Add-On

The vm-dhcp-controller add-on is not packed into the Harvester ISO, but you can download it from the expreimental-addons repository. You can install the add-on by running the following command:

kubectl apply -f https://raw.githubusercontent.com/harvester/experimental-addons/main/harvester-vm-dhcp-controller/harvester-vm-dhcp-controller.yaml

After installation, enable the add-on on the Dashboard screen of the Harvester UI or using the command-line tool kubectl.

Usage

On the Dashboard screen of the Harvester UI, create a VM Network.

Create an IPPool object using the command-line tool kubectl.

cat <<EOF | kubectl apply -f -
apiVersion: network.harvesterhci.io/v1alpha1
kind: IPPool
metadata:
  name: net-48
  namespace: default
spec:
  ipv4Config:
    serverIP: 192.168.48.77
    cidr: 192.168.48.0/24
    pool:
      start: 192.168.48.81
      end: 192.168.48.90
      exclude:
      - 192.168.48.81
      - 192.168.48.90
    router: 192.168.48.1
    dns:
    - 1.1.1.1
    leaseTime: 300
  networkName: default/net-48
EOF

Create a VM that is connected to the VM Network you previously created.
Wait for the corresponding VirtualMachineNetworkConfig object to be created and for the MAC address of the VM’s network interface to be applied to the object.

Check the .status field of the IPPool and VirtualMachineNetworkConfig objects, and verify that the IP address is allocated and assigned to the MAC address.

$ kubectl get ippools.network net-48 -o yaml                      
apiVersion: network.harvesterhci.io/v1alpha1
kind: IPPool
metadata:
  creationTimestamp: "2024-02-15T13:17:21Z"
  finalizers:
  - wrangler.cattle.io/vm-dhcp-ippool-controller
  generation: 1
  name: net-48
  namespace: default
  resourceVersion: "826813"
  uid: 5efd44b7-3796-4f02-947e-3949cb4c8e3d
spec:
  ipv4Config:
    cidr: 192.168.48.0/24
    dns:
    - 1.1.1.1
    leaseTime: 300
    pool:
      end: 192.168.48.90
      exclude:
      - 192.168.48.81
      - 192.168.48.90
      start: 192.168.48.81
    router: 192.168.48.1
    serverIP: 192.168.48.77
  networkName: default/net-48
status:
  agentPodRef:
    name: default-net-48-agent
    namespace: harvester-system
  conditions:
  - lastUpdateTime: "2024-02-15T13:17:21Z"
    status: "True"
    type: Registered
  - lastUpdateTime: "2024-02-15T13:17:21Z"
    status: "True"
    type: CacheReady
  - lastUpdateTime: "2024-02-15T13:17:30Z"
    status: "True"
    type: AgentReady
  - lastUpdateTime: "2024-02-15T13:17:21Z"
    status: "False"
    type: Stopped
  ipv4:
    allocated:
      192.168.48.81: EXCLUDED
      192.168.48.84: ca:70:82:e6:84:6e
      192.168.48.90: EXCLUDED
    available: 7
    used: 1
  lastUpdate: "2024-02-15T13:48:20Z"

$ kubectl get virtualmachinenetworkconfigs.network test-vm -o yaml
apiVersion: network.harvesterhci.io/v1alpha1
kind: VirtualMachineNetworkConfig
metadata:
  creationTimestamp: "2024-02-15T13:48:02Z"
  finalizers:
  - wrangler.cattle.io/vm-dhcp-vmnetcfg-controller
  generation: 2
  labels:
    harvesterhci.io/vmName: test-vm
  name: test-vm
  namespace: default
  ownerReferences:
  - apiVersion: kubevirt.io/v1
    kind: VirtualMachine
    name: test-vm
    uid: a9f8ce12-fd6c-4bd2-b266-245d8e77dae3
  resourceVersion: "826809"
  uid: 556440c7-eeeb-4daf-9c98-60ab39688ba8
spec:
  networkConfig:
  - macAddress: ca:70:82:e6:84:6e
    networkName: default/net-48
  vmName: test-vm
status:
  conditions:
  - lastUpdateTime: "2024-02-15T13:48:20Z"
    status: "True"
    type: Allocated
  - lastUpdateTime: "2024-02-15T13:48:02Z"
    status: "False"
    type: Disabled
  networkConfig:
  - allocatedIPAddress: 192.168.48.84
    macAddress: ca:70:82:e6:84:6e
    networkName: default/net-48
    state: Allocated

Check the VM’s serial console and verify that the IP address is correctly configured on the network interface (via DHCP).

vm-dhcp-controller Pods and CRDs

When the vm-dhcp-controller add-on is enabled, the following types of pods run:

Controller: Reconciles CRD objects to determine allocation and mapping between IP and MAC addresses. The results are persisted in the IPPool objects.
Webhook: Validates and mutates CRD objects when receiving requests (creation, updating, and deletion)
Agent: Serves DHCP requests and ensures that the internal DHCP lease store is up to date. This is accomplished by syncing the specific IPPool object that the agent is associated with. Agents are spawned on-demand whenever you create new IPPool objects.

The vm-dhcp-controller introduces the following new CRDs.

IPPool (ippl)
VirtualMachineNetworkConfig (vmnetcfg)

IPPool CRD

The IPPool CRD allows you to define IP pool information. You must map each IPPool object to a specific NetworkAttachmentDefinition (NAD) object, which must be created beforehand.

note

Multiple CRDs named “IPPool” are used in the Harvester ecosystem, including a similarly-named CRD in the loadbalancer.harvesterhci.io API group. To avoid issues, ensure that you are working with the IPPool CRD in the network.harvesterhci.io API group. For more information about IPPool CRD operations in relation to load balancers, see IP Pool.

Example:

apiVersion: network.harvesterhci.io/v1alpha1
kind: IPPool
metadata:
  name: example
  namespace: default
spec:
  ipv4Config:
    serverIP: 192.168.100.2 # The DHCP server's IP address
    cidr: 192.168.100.0/24 # The subnet information, must be in the CIDR form
    pool:
      start: 192.168.100.101
      end: 192.168.100.200
      exclude:
      - 192.168.100.151
      - 192.168.100.187
    router: 192.168.100.1 # The default gateway, if any
    dns:
    - 1.1.1.1
    domainName: example.com
    domainSearch:
    - example.com
    ntp:
    - pool.ntp.org
    leaseTime: 300
  networkName: default/example # The namespaced name of the NAD object

After the IPPool object is created, the controller reconciliation process initializes the IP allocation module and spawns the agent pod for the network.

$ kubectl get ippools.network example
NAME      NETWORK           AVAILABLE   USED   REGISTERED   CACHEREADY   AGENTREADY
example   default/example   98          0      True         True         True

VirtualMachineNetworkConfig CRD

The VirtualMachineNetworkConfig CRD resembles a request for IP address issuance and is associated with NetworkAttachmentDefinition (NAD) objects.

A sample VirtualMachineNetworkConfig object looks like the following:

apiVersion: network.harvesterhci.io/v1alpha1
kind: VirtualMachineNetworkConfig
metadata:
  name: test-vm
  namespace: default
spec:
  networkConfig:
  - macAddress: 22:37:37:82:93:7d
    networkName: default/example
  vmName: test-vm

After the VirtualMachineNetworkConfig object is created, the controller attempts to retrieve a list of unused IP addresses from the IP allocation module for each recorded MAC address. The IP-MAC mapping is then updated in the VirtualMachineNetworkConfig object and the corresponding IPPool objects.

note

Manual creation of VirtualMachineNetworkConfig objects for VMs is unnecessary in most cases because vm-dhcp-controller handles that task during the VirtualMachine reconciliation process. Automatically-created VirtualMachineNetworkConfig objects are deleted when VirtualMachine objects are removed.