How to fix failed DIAG-CONTROL Check Sequence error
In-case you run in to the error stated above “failed DIAG-CONTROL Check Sequence” there are things you can try to solve this issue, these fixes can vary from as simple as re-coding the modules to a different firmware so it would be supported and recognized correctly, to determining whether or not the equipment itself is damage or going through the painstaking process of updating your equipment.
Understanding the Why?
First, before we try to fix the issue, we must look into what could be causing such issues in your Fortinet equipment. The reason why this type of error can appear may vary, it could be that the switch/router is running on a older version, or that the transceivers or cables are programmed with a different coding that is unsupported in that exact device.
Compatibility
- •Ensure that the DAC cable is supported by your Fortinet device.
Damage to the cable itself
- •Check for any visible damage to the DAC cable or the SFP module.
- •Re-seat the DAC cable by removing and reinserting it firmly.
- •Try a different port to see if the issue follows the DAC or stays on the same port.
Firmware (Coding)
- •Ensure that your Fortinet device is running the latest firmware. Some versions have bug fixes related to DAC connectivity.
- •If you’re using an older firmware, check Fortinet’s release notes for known issues related to DACs.
Fortinet equipment
- •If the problem persists across different cables and firmware updates, there may be a hardware issue with the Fortinet device.
- •Contact Fortinet Support to check if there are known hardware failures for your model.
Fixing the problem
We would suggest that you contact our support team for a clear and definitive analysis of your exact situation. As the problems can vary, and in each instance of an error, there are many things at play. We will gladly try to help you crack the problem and find a solution to it. So, in case you have this type of error, don’t hesitate to ask, we will help!
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Direct Attach Cables (DAC) – 10G to 800G
Direct Attach Copper (DAC) cables deliver high-speed connectivity for data centers and network equipment rooms where cost efficiency and low power consumption are priorities. These pre-terminated copper assemblies eliminate the need for separate transceivers, reducing both equipment costs and power draw compared to optical solutions. EdgeOptic's DAC portfolio spans 10G to 800G speeds, with passive cables reaching up to 7 meters for lower speeds and 3 meters for higher bandwidths. For connections requiring extended reach without transitioning to fiber, our active DAC options provide signal amplification to maintain data integrity over longer distances. When connecting equipment operating at different speeds—such as 100G switches to 25G servers or 40G infrastructure to 10G devices—our breakout DAC cables split high-bandwidth connections into multiple lower-speed ports, simplifying network architecture and reducing port costs. All EdgeOptic DAC cables are coded for compatibility with major networking vendors including Cisco, Juniper, HPE, Dell, and Mellanox. Our engineering team can also provide custom configurations with different vendor coding on each end—ideal for mixed-vendor environments in data center deployments. Contact us for compatibility questions or custom requirements.
Compatible Fortinet Transceivers
This section covers Fortinet Compatible Transceivers including 10G SFP+, 100G, 50G, 40G, and DAC cables for Fortinet Fortigate & Fortiswitch devices. We offer compatible optical transceivers for Fortinet network security systems. Our Fortigate Transceiver and Fortiswitch Transceiver compatible modules are widely used among network engineers.