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Solved: How do I configure QOS queue for control traffic on FortiSwitch?

This article describes what is control traffic, which QoS queue is used in FortiSwitch for control traffic and a few protocol examples that are included in the control plane.


FortiSwitch and FortiGate version 6.4.x and above


Control plane traffic includes traffic generated, processed, and forwarded by the FortiSwitch CPU.

Some protocol examples are MCLAG, loop guard, OSPF, BFD, RIP, ISIS, VRRP, ARP, EAPOL, MRP, DHCP, IGMP, capwap, fortilink, lldp.

There are some cases where the FortiSwitch CPU will handle non-control traffic.


If hardware routing is not supported or the hardware table is full, normal L3 routed traffic would flow through the CPU)

For STP from a 3rd party (or any unit), BPDU would traverse both control and dataplane.

In the hardware (dataplane), BPDUs higher relative priority is given than other protocols which allow the switch to react quickly to changes in the network topology.

The CPU then handles the BPDU traffic in the spanning tree daemon. This process also has a higher relative priority for similar reasons.

There are 8 QoS queues in FortiSwitch 0 to 7, queue 7 is used for control traffic.

To further explain, the traffic on the FortiSwitch ports should be sent into and out Q7.

However, when traffic is delivered to the local CPU (via protocol trap) those priorities are shuffled internally on FortiSwitch by design.

FortiSwitch split out different traffic types into different Queues with different rate limits.

These are not the same Q as we would see on switch ports.

Alex Lim is a certified IT Technical Support Architect with over 15 years of experience in designing, implementing, and troubleshooting complex IT systems and networks. He has worked for leading IT companies, such as Microsoft, IBM, and Cisco, providing technical support and solutions to clients across various industries and sectors. Alex has a bachelor’s degree in computer science from the National University of Singapore and a master’s degree in information security from the Massachusetts Institute of Technology. He is also the author of several best-selling books on IT technical support, such as The IT Technical Support Handbook and Troubleshooting IT Systems and Networks. Alex lives in Bandar, Johore, Malaysia with his wife and two chilrdren. You can reach him at [email protected] or follow him on Website | Twitter | Facebook

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