Troubleshooting Tip: 25 Gigabit Ethernet connection between FortiGate and Cisco Nexus

[caunon]

Description

This article describes how to fix 25 Gigabit Ethernet connection between FortiGate and Cisco Nexus.

Scope

• FortiOS 7.2.
• FortiGate with 25 Gigabit Ethernet interface.
• FortiGate with Fortinet : FN-TRAN-SFP28-SR model to connect to Cisco Nexus via fiber optic cable.
• Cisco Nexus with 25 Gigabit Ether net interface.
• Cisco Nexus with Cisco : SFP-10/25G-CSR-S model to connect to FortiGate via fiber optic cable.
• The connection between FortiGate and Cisco Nexus can be only the single interface or a link aggregation interface.

Solution

• In this case, a FortiGate unit with 25Gigabit Ethernet interface is connected to a Cisco Nexus Ethernet interface with the default settings, but the interface is still not up for both sites.
• At the Cisco Nexus site, a user receives an error when trying to correct the settings of the 25 Gigabit Ethernet interface with the following:

fec rs-ieee

The error message:

"ERROR: FEC validation failed on ethX/Y due to incompatible configured speed or transceiver type"

(X/Y is the Cisco Nexus interface.)

The solution to fix the issue:

In FortiGate:

config system interface
    edit <interface name>
        set speed 25000full
        set forward-error-correction c174-fc-fec
    next
end

The same configuration should be performed on the Cisco Nexus side as well.