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Activate and check DHCP

Before you start

  • You need the admin role and permission to restart the Linux node.
  • You need a saved scope and the required host privileges.
  • You need a copy of the old DHCP configuration and its final lease data.

CAUTION: Existing leases stay valid until they expire. Prevent kudurru from reusing addresses that the old server assigned to other clients.

1. Prepare the cutover

  1. Save the old server's options and reservations.
  2. Open DNS > DHCP in kudurru.
  3. Turn on Enable DHCP after restart.

The DHCP page with Enable DHCP after restart on, a Restart required notice and the saved scope.

Figure 1. The saved enabled state does not change the running service.

The notice Restart required means that the current allocator has not changed. The scope can show Changes pending or Saved, not running.

2. Switch the service

  1. Stop the old DHCP service.

  2. Export its final leases if your migration uses an import.

  3. Prevent client DHCP traffic from reaching kudurru until the import completes.

  4. Restart the kudurru node.

    For Docker, use docker restart kudurru. For systemd, use sudo systemctl restart kudurru.

  5. Import the final leases from the scope page, if needed.

  6. Allow client DHCP traffic to reach kudurru.

Use a nonoverlapping pool or wait for old leases to expire if you cannot import them. The import guide lists supported formats. Do not start two independent allocators on the same pool.

3. Test one client

  1. Open DNS > DHCP.
  2. Confirm that the scope says Running.
  3. Renew the DHCP lease on one test client.
  4. Open the scope and find the client in Leases.
  5. Check the client's address, subnet mask, gateway and DNS server.
  6. Run nslookup example.com on the client.

The running scope's Leases section with addresses, MAC addresses, hostnames, lease states and expiration times.

Figure 2. A bound client appears as Leased.

To renew, use the network settings of the test client:

ClientAction
WindowsRun ipconfig /renew in a terminal
macOSOpen the network details, select TCP/IP, then click Renew DHCP Lease
Linux desktopUse automatic IPv4 (DHCP), then disconnect and reconnect the network

The address comes from your pool or a reservation. The DNS server matches your node. If registration is on, query the client's full local name too.

Check the result

Restart kudurru and renew the test client's lease again. Confirm that its address and DNS still work. Test a second client before you move the rest.

If startup fails, use DHCP diagnosis. If no lease appears, check UDP ports 67 and 68, the interface and any relay settings.

For rollback, stop kudurru DHCP before you restore the old service. On SQLite, turning off the switch also needs a restart. Account for every unexpired kudurru lease in the old server's pool before you restart it.

Source: docs/guide/dhcp/activate.md