We've been running a fleet of FortiGate 200D appliances for several years, primarily as VPN concentrators and for basic segmentation. Over the past nine months, we've experienced persistent, intermittent interface flapping on the physical ports across multiple units. The issue manifests on different interfaces, not tied to a specific port, and occurs across different firmware versions (we've tried 6.0.15, 6.2.13, and 6.4.14 in an attempt to resolve it).
The flapping causes brief but disruptive outages to connected services, triggering spanning-tree reconvergence events in the adjacent switches (Cisco and Aruba). We've eliminated the obvious external factors:
* Replaced transceivers and cabling.
* Tested with adjacent switch ports set to hard-coded speed/duplex.
* Monitored for CRC errors or voltage anomalies on the switch side (none found).
* The issue persists even when the interface is in a dedicated VDOM with minimal configuration.
Our internal hypothesis is a hardware-level fault, perhaps related to the ASIC or PHY components on this particular series, given the pattern across multiple units of the same model. Before we engage Fortinet TAC and potentially initiate a costly, multi-unit RMA process—which would involve significant labor for us in reconfiguration and testing—I wanted to consult the community.
My specific questions are:
* Is this a documented or known issue with the 200D series hardware revision that we may have missed in the release notes or knowledge base?
* Has anyone successfully resolved a similar issue through a specific firmware downgrade or configuration change that isn't part of the standard interface setup?
* If this is a confirmed hardware fault, what was your experience with the RMA process for this model? Were replacement units a different hardware revision, and did they resolve the instability?
I am particularly interested in the long-term reliability post-resolution, as our total cost of ownership calculation for this platform is being severely impacted by these unexplained operational failures. Any detailed technical or procedural insights would be appreciated.
-pete
Read the fine print
Been there. Your hardware hypothesis is likely correct, but before you call TAC, check the power supplies. Those units are old enough that marginal power delivery can cause exactly this kind of phantom, cross-port flapping. It presents as an ASIC or PHY issue but it's just the board starving. Seen it on other aging gear.
If you've already swapped PSUs, then yeah, it's probably the backplane. Good luck with TAC. They'll make you jump through every diagnostic hoop again.
More dashboards != better ops