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New Contributor

LACP Between Mikrotik & Fortigate Problem

Hi guys,
I have strange problem. In environment of my client there are two Mikrotik CCR1016-12G and one Fortigate 600D. For a scenario I've connected 4 interfaces from Fortigate to two Mikrotiks and admin of Fortigate configured two Link Aggregation (LACP) on it and placed two interfaces in each them then I configured one bonding interface on each Mikrotik. My problem is in one of Mikrotik bonding interface is up and also in Fortigate LACP interface is up but when I set IP on bonding interface I couldn't ping IP of Fortigate LACP interface. But the same config on another Mikrotik works without problem. I will appreciate if you help me to solve this problem.
Best Regards.

Contributor III

1. Check the MTU (Maximum Transmission Unit) size on the bonding interface of the Mikrotik and the LACP interface of the Fortigate. Make sure they match, as a mismatched MTU can cause packet fragmentation and communication issues.

2. Verify that the VLAN configuration is the same on both devices, if VLANs are being used. If the VLAN configuration is incorrect or missing on either device, this could cause communication issues.

3. Check the firewall rules on both devices to ensure that they allow traffic to pass between the bonding interface and the LACP interface.

4. Verify that the speed and duplex settings on the interfaces are correctly configured and match on both devices. A mismatch in these settings can cause connectivity issues.

5. Check for any errors or warnings in the system logs on both devices. These can provide valuable insights into the root cause of the issue.

6. Try temporarily disabling any firewall or security features on both devices to see if this resolves the issue. If it does, you may need to adjust the settings or configuration of these features to allow traffic to pass through.

New Contributor

Thanks a lot Christian. I will check what you said. I wonder why everything OK on first Mikrotik and LACP-1 on Fortigate but same configuration doesn't work on second Mikrotik and LACP-2.


Make sure on LACP-2 you also permit ping (in the `Administrative Access` section). Can be a probable cause.


Ping is enabled on LACP-2.Is there any additional configuration for second LACP in Fortigate? for example I must set vlan or zone for second LACP.