Fortiswitch FS-124E to Cisco 3750X via SFP - No Connection

[Joe667]

I have a new FS-124E running Firmware 6.2.1 and am trying to communicate with a Cisco 3750X running IOS 12.2(55)SE3 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 both set as trunks. The port config on the Cisco RJ45 is identical to the config on the SFP port on the Cisco, with one exception. The link on the Cisco SFP port is down/down unless I enter the speed nonegotiate command. This brings up the link light on the Cisco and the show interface for the SFP port is up/up. Still no communication. 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.

[Joe667]

SOLUTION

It appears that in 6.2 there is a problem with the trunking over SFP. I solved the problem by leaving my SFP port out of the trunk setup and adding all VLANs to the Allowed VLANs for that particular port.

[sel18]

Hello @Joe667 

please i have the same issue with the same situation, i have Fortiswitch 124E connected via fiber to cisco 3750 after adding the command speed nonegotiate the link be UP/UP but still no traffic between the two switch. how can i solve this issue please ?

thanks in advance 

[desertcactus]

I had the exact same issue. I resolved it by changing lldp to the default profile instead of the one that uses auto-isl, disabled fortilink detection, disabled stp and edge port. Once all of that was done, I changed speed to auto and the link came up without issue. Even though cisco side was set to 1000-full. All settings were changed on the Fortiswitch side.