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MikroTik RouterOS RoMON: Router Management Overlay Network

MikroTik RouterOS RoMON: Router Management Overlay Network

Section titled “MikroTik RouterOS RoMON: Router Management Overlay Network”

RouterOS Version: 6.x / 7.x (v7.17+ has improved switch chip handling) Difficulty: Intermediate Estimated Time: 20 minutes

Overview

Section titled “Overview”

RoMON (Router Management Overlay Network) creates an independent Layer 2 management network that operates regardless of your IP configuration. When routing is broken, firewalls are misconfigured, or IP addresses are wrong, RoMON still works - allowing you to access and fix devices that would otherwise be unreachable.

Key benefits:

  • Works when IP is broken - Access devices even with misconfigured routes or firewalls
  • Hop through devices - Connect to a distant router through intermediate MikroTik devices
  • No VPN required - Direct Layer 2 management path
  • Discovery - Find all RoMON-enabled devices on the network

How it works: RoMON uses special Layer 2 frames (EtherType 0x88bf, multicast MAC 01:80:c2:00:88:bf) to create a virtual overlay network. Each device gets a RoMON ID (MAC address format), and devices forward RoMON traffic independently of normal switching/routing.

Important: RoMON is MikroTik-proprietary - it only works between MikroTik devices.

Configuration Steps

Section titled “Configuration Steps”

Step 1: Enable RoMON

Section titled “Step 1: Enable RoMON”
/tool romon set enabled=yes
Section titled “Step 2: Set a Secret (Recommended)”

The secret authenticates RoMON neighbors and prevents accidental peering with unknown devices:

/tool romon set secrets=YourSecretPassword

Important: Use the same secret on all devices that should communicate via RoMON.

Step 3: Verify Configuration

Section titled “Step 3: Verify Configuration”
/tool romon print

Expected Output:

        enabled: yes
             id:
     current-id: 6C:3B:6B:48:0E:8A
        secrets: YourSecretPassword

The current-id shows the automatically assigned RoMON ID (derived from MAC address).

Step 4: Configure Ports (Optional)

Section titled “Step 4: Configure Ports (Optional)”

By default, RoMON operates on all interfaces. To restrict to specific interfaces:

# Remove the default "all" entry
/tool romon port remove [find interface=all]


# Add specific interfaces
/tool romon port add interface=ether1 cost=100
/tool romon port add interface=ether2 cost=100

Using RoMON

Section titled “Using RoMON”

Discover RoMON Devices

Section titled “Discover RoMON Devices”

Find all RoMON-enabled devices on the network:

/tool romon discover

Example Output:

 # ADDRESS           COST    HOPS   PATH                          AGE
 0 6C:3B:6B:48:0E:8A    0       0                                   1s
 1 6C:3B:6B:48:0E:8B  100       1   6C:3B:6B:48:0E:8A               3s
 2 6C:3B:6B:48:0E:8C  200       2   6C:3B:6B:48:0E:8A,6C:3B:6...   5s
  • ADDRESS - RoMON ID of discovered device
  • COST - Total path cost to reach device
  • HOPS - Number of intermediate devices
  • PATH - RoMON IDs of intermediate devices

Ping a RoMON Device

Section titled “Ping a RoMON Device”

Test connectivity to a specific device:

/tool romon ping id=6C:3B:6B:48:0E:8B count=5

Connect via SSH

Section titled “Connect via SSH”

Open a terminal session through RoMON:

/tool romon ssh 6C:3B:6B:48:0E:8B user=admin

Connect via WinBox

Section titled “Connect via WinBox”

In WinBox, use the RoMON tab at the bottom of the connect window, or from command line:

winbox.exe --romon 192.168.88.1 6C:3B:6B:48:0E:8B admin ""

Where:

  • 192.168.88.1 - IP of the RoMON “entry point” router you can reach
  • 6C:3B:6B:48:0E:8B - RoMON ID of the target device
  • admin "" - Username and password

Port Configuration

Section titled “Port Configuration”

Port Properties

Section titled “Port Properties”
PropertyDefaultDescription
interface-Interface name or interface-list
cost100Path metric (lower = preferred)
disablednoDisable RoMON on this port
secrets-Port-specific secrets (overrides global)

View Port Configuration

Section titled “View Port Configuration”
/tool romon port print

Default Output:

Flags: X - disabled
 #   INTERFACE   COST     SECRETS
 0   all         100

Adjust Port Cost

Section titled “Adjust Port Cost”

Prefer certain paths by lowering their cost:

/tool romon port set [find interface=ether1] cost=50

Disable RoMON on Specific Interfaces

Section titled “Disable RoMON on Specific Interfaces”
/tool romon port add interface=ether1-wan disabled=yes

Or remove from participation entirely:

/tool romon port remove [find interface=ether1-wan]

Security with Secrets

Section titled “Security with Secrets”

How Secrets Work

Section titled “How Secrets Work”

Secrets authenticate RoMON messages using MD5 hashing. Devices only become neighbors if they share at least one common secret.

Important: Secrets provide authentication, not encryption. Use SSH or secure WinBox for encrypted management sessions.

Multiple Secrets (Rolling Updates)

Section titled “Multiple Secrets (Rolling Updates)”

You can configure multiple secrets to allow gradual migration:

/tool romon set secrets=OldSecret,NewSecret

Devices accept messages hashed with any configured secret, allowing you to:

  1. Add new secret to all devices
  2. Remove old secret from all devices

This prevents service interruption during secret rotation.

Per-Port Secrets

Section titled “Per-Port Secrets”

Override global secrets on specific ports:

/tool romon port set [find interface=ether5] secrets=SpecialSecret

Common Configuration Scenarios

Section titled “Common Configuration Scenarios”

Scenario 1: Basic RoMON Network

Section titled “Scenario 1: Basic RoMON Network”

Enable RoMON on all devices with a shared secret:

/tool romon set enabled=yes secrets=MyNetworkSecret

Repeat on all MikroTik devices.

Scenario 2: Restrict RoMON to Management VLAN

Section titled “Scenario 2: Restrict RoMON to Management VLAN”

Only allow RoMON on the management VLAN interface:

# Remove default all-interface entry
/tool romon port remove [find interface=all]


# Add only management interface
/tool romon port add interface=vlan-mgmt cost=100

Scenario 3: Hub-and-Spoke Topology

Section titled “Scenario 3: Hub-and-Spoke Topology”

Configure lower costs on backbone links:

# On backbone interfaces
/tool romon port set [find interface=sfp1] cost=10


# On access interfaces
/tool romon port set [find interface=ether1] cost=100

Scenario 4: Exclude WAN from RoMON

Section titled “Scenario 4: Exclude WAN from RoMON”

Prevent RoMON traffic on internet-facing interfaces:

/tool romon port add interface=ether1-wan disabled=yes

Verification

Section titled “Verification”

Check 1: Verify RoMON is Enabled

Section titled “Check 1: Verify RoMON is Enabled”
/tool romon print

Expected: enabled: yes and current-id populated.

Check 2: Discover Neighbors

Section titled “Check 2: Discover Neighbors”
/tool romon discover

Expected: List of all RoMON-enabled devices on the network.

Check 3: Test Connectivity

Section titled “Check 3: Test Connectivity”
/tool romon ping id=TARGET_ROMON_ID count=5

Expected: Successful replies.

Check 4: Verify Port Configuration

Section titled “Check 4: Verify Port Configuration”
/tool romon port print

Expected: Correct interfaces enabled with appropriate costs.

Troubleshooting

Section titled “Troubleshooting”

Problem: “Device not appearing in discover”

Section titled “Problem: “Device not appearing in discover””

Causes:

  • RoMON not enabled on target device
  • Different secrets configured
  • No Layer 2 path between devices
  • RoMON disabled on intermediate ports

Solution:

  1. Verify RoMON enabled on target: /tool romon print
  2. Check secrets match on all devices
  3. Verify physical connectivity
  4. Check port configuration on intermediate devices

Problem: “RoMON ping works but SSH/WinBox fails”

Section titled “Problem: “RoMON ping works but SSH/WinBox fails””

Cause: RoMON provides connectivity, but authentication fails at the application level.

Solution:

  1. Verify username and password
  2. Check if the target device allows the connection (MAC server settings)
  3. Try different authentication methods

Problem: “RoMON stopped working after upgrade to 7.17+”

Section titled “Problem: “RoMON stopped working after upgrade to 7.17+””

Cause: RouterOS 7.17 changed how switch chips handle RoMON packets.

Solution:

  1. Devices with ACL-capable switch chips should work automatically
  2. For non-ACL switches, ensure CPU and RoMON traffic are in the same VLAN
  3. Check bridge configuration for hardware offloading issues

Problem: “Intermittent RoMON connectivity”

Section titled “Problem: “Intermittent RoMON connectivity””

Cause: Unstable Layer 2 path or STP topology changes.

Solution:

  1. Verify physical connections
  2. Check for STP reconvergence events
  3. Consider adjusting port costs to prefer stable paths

Problem: “Neighbors appear with wrong cost”

Section titled “Problem: “Neighbors appear with wrong cost””

Cause: Port costs not configured consistently.

Solution:

/tool romon port print

Verify costs are set appropriately. Lower cost = preferred path.

Common Pitfalls

Section titled “Common Pitfalls”

1. Forgetting to Set Secrets

Section titled “1. Forgetting to Set Secrets”

Wrong:

/tool romon set enabled=yes
# No secret - devices may peer with unknown routers

Right:

/tool romon set enabled=yes secrets=SecurePassword

2. Leaving RoMON Enabled on WAN

Section titled “2. Leaving RoMON Enabled on WAN”

Risk: RoMON traffic visible to upstream network.

Solution:

/tool romon port add interface=ether1-wan disabled=yes

3. Mismatched Secrets

Section titled “3. Mismatched Secrets”

Problem: Devices can’t discover each other.

Solution: Ensure identical secrets on all devices that should communicate:

/tool romon set secrets=SameSecretEverywhere

4. Expecting Encryption from RoMON

Section titled “4. Expecting Encryption from RoMON”

Wrong assumption: “RoMON secret encrypts my management traffic”

Reality: Secrets only authenticate neighbors. Use SSH or secure WinBox for encrypted sessions.

5. Not Considering Path Costs

Section titled “5. Not Considering Path Costs”

Problem: Traffic takes suboptimal paths.

Solution: Set lower costs on preferred/faster links:

/tool romon port set [find interface=sfp1] cost=10

Security Considerations

Section titled “Security Considerations”
  1. Always use secrets - Prevents unauthorized devices from joining your RoMON network
  2. Use SSH or secure WinBox - RoMON doesn’t encrypt management traffic
  3. Disable on untrusted interfaces - Don’t expose RoMON on WAN or guest networks
  4. Rotate secrets periodically - Use multiple secrets during transitions
  5. Limit port participation - Only enable on necessary interfaces

Limitations

Section titled “Limitations”
  • MikroTik only - Won’t work with other vendors
  • No encryption - Authentication only; use SSH/secure WinBox
  • Layer 2 dependent - Requires physical or L2 tunnel connectivity
  • Switch chip behavior - Some chips may require specific configuration (v7.17+)
  • Not a replacement for proper IP management - Use as backup access method
Section titled “Related Features”
  • MAC Server (/tool mac-server) - MAC-based WinBox/Telnet access
  • Neighbor Discovery (/ip neighbor) - Find devices on local network
  • The Dude - Network monitoring (integrates with RoMON)
  • WinBox - GUI management tool with RoMON support

References

Section titled “References”
Section titled “Related Topics”

Device Discovery

Section titled “Device Discovery”

Security

Section titled “Security”

Network Management

Section titled “Network Management”