Catalyst C9300X-24Y resets FEC to auto when an SFP-H25G-CU2M DAC is inserted, breaking the link to a FortiGate
4
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
Comments 2
A respondent asked for the exact switch model and software, noted that on multi-gigabit ports supporting different module types the warning may be expected, asked whether the FortiGate supports 25G, and later suggested trying a 10G SFP module to prove the issue is not DAC compatibility with Fortinet.
Another respondent asked whether the SFP-H25G-CU2M is Cisco-sourced (a non-Cisco cable could be the cause), explained that FEC negotiation is part of the port auto-negotiation exchange, and suggested 'no negotiation auto' on Twe1/0/23 followed by hard-coding the port parameters. No confirmation of a fix was posted.