Catalyst C9300X-24Y resets FEC to auto when an SFP-H25G-CU2M DAC is inserted, breaking the link to a FortiGate
The poster connects a Cisco Catalyst C9300X-24Y to a FortiGate firewall with a 25G SFP-H25G-CU2M DAC. Whenever the DAC is inserted the switch logs '%PLATFORM_PM-6-MODULE_INSERTED: SFP module inserted with interface name Twe1/0/23' followed by '%PLATFORM_PM-6-DIFFERENT_MODULE_INSERTED: Warning: SFP module inserted in to the interface Twe1/0/23 differs from the previously inserted one. The port's fec configuration will be set to the default.' The FEC setting reverts to auto, which the FortiGate does not support, so the link never comes up. Both devices were confirmed 25G-capable by looping two of their own ports with the same cable type; only the cross-vendor combination fails.
- Hardware: Cisco Catalyst C9300X-24Y, Fortinet FortiGate firewall
- Transceivers: SFP-H25G-CU2M
- Form factor: SFP28, DAC
Symptoms / messages:
%PLATFORM_PM-6-MODULE_INSERTED: SFP module inserted with interface name Twe1/0/23
%PLATFORM_PM-6-DIFFERENT_MODULE_INSERTED: Warning: SFP module inserted in to the interface Twe1/0/23 differs from the previously inserted one. The port's fec configuration will be set to the default.
FEC reverts to auto on module insertion
no 25G link to FortiGate
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Comments 2
What's the exact switch model and software version? On multi-gigabit ports that support different module types, that warning can actually be expected. Does the FortiGate even support 25G? Also, try a 10G SFP module - that would prove the issue isn't DAC compatibility with Fortinet.
Is the SFP-H25G-CU2M actually Cisco-sourced? A non-Cisco cable could be causing this. FEC negotiation is part of the port auto-negotiation exchange, so try 'no negotiation auto' on Twe1/0/23 and then hard-code the port parameters.