FortiSwitch 224E-POE to Cisco 2960x via SFP does not work.

[johnevans]

I have a new FS-224E running Firmware 6.2.1 and am trying to communicate with a Cisco 2960X running IOS 15.2(4)E7 via SFP ports. I have configured the FortiSwitch as a stand-alone. Connecting from RJ45 to RJ45 between the switches, the communication is fine and my configs work. The ports used for communication are set as a trunk on the Cisco and standard interface on the FortiSwitch with the native VLAN matching and all VLANs allowed. The port config on the Cisco RJ45 is identical to the config on the SFP port on the Cisco. When hooked up via SFP ports the link on the Cisco SFP port is down/down. The lights on the FortiSwitch do light up without issue but not he on the Cisco. I have confirmed my FortiSwitch transceiver is on the compatibility list. I am using a proven fiber cable, a proven Cisco transceiver, and a proven port on the Cisco switch. All diagnostic commands show no alarms or errors. The log provides no clues. I have tested FortiSwtch to FortiSwith and it works and Cisco to Cisco and it works. Just not FortiSwitch to Cisco.

[johnevans]

I figured it out. The FortiSwitch ports were statically set to Full\Duplex where the Cisco wanted Auto. Only the SFPs on the FortiSwitch are statically set the rest arent by default. I am certain the smart move is to set both to Full and Duplex and not be on auto.

[johnevans]

I am adding some more context here for everyone else. We just had a similar problem but with a different fix. We connected a Cisco with those multiple-use ports with an SFP stacked over a gigabit copper RJ45 port. The speed commands weren't available, and although the copper connector would work, the SFP wouldn't. It would show link lights on the Fortiswitch 1048e but no lights on the Cisco. 

So we added the "media-type sfp" command to the Cisco interface, which let us use the "speed nonegotiate" command.

After that, they lit up and connected, and our EtherChannel started working.

Just putting this here for future John when we do another search for this probably two years later and find this original post again. You are welcome, future John.