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Troubleshooting DHCP: Why Isn't My Subscriber Getting an Address?

Jennifer Trower Updated by Jennifer Trower

Read Time: 4 mins

DHCP issues in Sonar usually come from one of a few recurring patterns: a missing DHCP lease script on MikroTik, a Serviceable Address change, a stale DHCP server entry, an egress IP whitelisting issue, or a mixed PPPoE and DHCP network configuration.

This article helps you match the issue you are seeing to the most likely cause and provides troubleshooting steps for each scenario. For initial setup, see DHCP Delivery.

Permissions

Before getting started with troubleshooting, your user roles will need to be adjusted to account for the permissions required to view and diagnose DHCP issues.

If you're a Super Admin, you already have full access and no changes are needed. To learn more, see the Roles and Permissions article.
Entity Permission Why It's Required
DHCP Server View all DHCP servers View DHCP server records to confirm lease script presence and identify stale entries.
IP Address Management Create an element in IPAM Re-create an IPAM element when reattaching IP assignments to a new Serviceable Address record.
IP Address Management Update an element in IPAM Update IPAM elements when cleaning up stale subnet or pool assignments found during diagnosis.
IP Assignment View all IP assignments Confirm IP assignments are properly linked to the new Serviceable Address record after an address change.
Address View serviceable addresses Review the subscriber's Serviceable Address record for changes that may have interrupted DHCP delivery.
Account View accounts and related entities Open the subscriber's account to review services, lease history, and account-level logs.
Access Log Read view history Review the audit log for Serviceable Address changes around the time the issue began.

Troubleshooting Steps

Start with the symptom that best matches what you are seeing. Step 1 resolves most MikroTik-based DHCP issues on its own.

Symptom-to-Cause Quick Reference

Symptom Most Likely Cause Go To
MikroTik subscribers not receiving leases in Sonar DHCP lease script missing Step 1
Subscriber recently moved or address was changed Serviceable Address mismatch Step 2
All subscribers on a subnet are not working Stale or orphaned DHCP server entry Step 3
Sonar shows no DHCP communication at all Egress IP not whitelisted Step 4
Mixed PPPoE and DHCP network not behaving as expected Service profile configuration Step 5
Step 1: Confirm the DHCP Lease Script Is Installed

Use this step when dynamic leases are not appearing in Sonar even though the subscriber is connected and receiving an IP from the MikroTik.

The most common cause is that the DHCP lease script has not been installed on the MikroTik DHCP server. Without it, MikroTik does not notify Sonar when a lease is assigned or removed.

To troubleshoot:

  1. On your MikroTik, navigate to IP > DHCP Server.
  2. Open the DHCP server configuration for the relevant pool.
  3. Confirm the Lease Script field contains the Sonar lease script.
  4. If the field is empty or contains an outdated script, install the current version from DHCP Delivery.
  5. Replace api_key and url with your API key and Sonar URL.

For more context on how the script integrates with Sonar's DHCP handling, see MikroTik: Setting Up a Sonar Controlled DHCP Server.

Step 2: Verify the Serviceable Address

Use this step when a subscriber who was previously working stops receiving an address, and the issue began around the time of a move, address correction, or account edit.

Serviceable Address changes, including removing and re-adding the same address, can interrupt DHCP delivery. Inventory and IP assignments are tied to the Serviceable Address record.

To troubleshoot:

  1. Open the subscriber's account in Sonar.
  2. Review the audit log for any Serviceable Address change, addition, or removal around the time the issue began.
  3. If the address was dropped and re-added, confirm the inventory and IP assignments are correctly associated with the new address record.
  4. If inventory or assignments are missing, reattach them and retry.
Step 3: Check for Stale DHCP Server Entries

Use this step when subscribers on a specific subnet or DHCP pool stop receiving addresses, often after a configuration change or migration.

Bad or orphaned entries in Sonar's DHCP Server list can cause issues across an entire subnet.

To troubleshoot:

  1. In Sonar, navigate to Settings > Networking > DHCP Servers.
  2. Review the list for entries that no longer correspond to active hardware, IPs, or pools.
  3. Remove stale entries.
  4. Confirm the affected subnet is still properly mapped to a valid DHCP server.
Step 4: Confirm Sonar's Egress IPs Are Whitelisted

Use this step when Sonar shows no DHCP traffic at all from your network, even though the DHCP server is running.

To troubleshoot:

  1. Refer to How Sonar Communicates - Egress IPs Explained for the current list of Sonar egress IPs.
  2. Confirm each is permitted on your DHCP server and any firewalls between your DHCP server and Sonar.
  3. If you recently changed firewalls or moved infrastructure, re-verify the whitelist.
Step 5: Mixed PPPoE and DHCP Networks

Use this step when your network uses a mix of PPPoE and DHCP provisioning, often as part of a migration from legacy hardware, and services are not behaving consistently.

When some subscribers authenticate using PPPoE and others using DHCP for the same logical service, the authentication difference may require distinct service profiles in Sonar.

To troubleshoot:

  1. Review whether the affected subscribers are on PPPoE or DHCP.
  2. Confirm the service assigned to each subscriber matches the profile expected for their authentication method.
  3. If a single service profile is being used for both PPPoE and DHCP subscribers, consider splitting it into two profiles, one per authentication method.
  4. Migrate subscribers to the correct profile based on their actual authentication method.

Sonar Internal Behavior to Know

Sonar synchronizes DHCP data every 60 seconds. Recent lease changes may take up to one minute to appear in Sonar. Under heavy load, synchronization can fall slightly behind.

Validation Workflow Note

When validating MikroTik credentials in Sonar, you may see a Validation Failed message with the status "This is not a compatible RouterOS service." If you see this, wait two minutes and refresh the page. Validation usually succeeds on the second attempt.

When to Open a Support Ticket

Open a support ticket after completing the relevant troubleshooting step if the issue continues.

Include the following information:

  1. The symptom you are seeing.
  2. The step in this article you completed.
  3. Account ID.
  4. MAC address of the subscriber device.
  5. Subnet and DHCP pool the subscriber is on.
  6. A snippet of the MikroTik DHCP log around the failed lease.
  7. Whether the DHCP lease script is installed.
  8. Any Serviceable Address changes around the time the issue began.

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