FEC has the following restrictions:
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FEC is supported on the DS-X9748-3072K9, DS-X9648-1536K9, DS-X9334-K9, and DS-X9448-768K9 modules in the Cisco MDS 9700 Series
switch. FEC is also supported on the Cisco MDS 9132T, MDS 9220i, MDS 9396S, MDS 9148T, and MDS 9396T switches.
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FEC fallback1 is not supported on the Cisco MDS 48-Port 64-Gbps Fibre Channel Switching Module (DS-X9748-3072K9) and Cisco MDS 9700 48-Port
32-Gbps Fibre Channel Switching Module (DS-X9648-1536K9) when their interfaces are configured at 16-Gbps Fibre Channel fixed
speed. However, FEC fallback is supported on the Cisco MDS 9700 48-Port 16-Gbps Fibre Channel Switching Module (DS-X9448-768K9)
when its interfaces are configured at 16-Gbps Fibre Channel fixed speed.
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Modifying the FEC configuration briefly disrupts traffic on the port.
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FEC cannot be configured when auto speed is selected for operating speeds 2000/4000/8000/16000. However, FEC is always enabled
on ports running at 32-Gbps and higher speeds but no configuration is required.
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Ports operating at 32 Gbps or higher speeds automatically negotiate FEC because FEC is required at those speeds. No FEC configuration
is necessary as the switchport fec and switchport fec tts commands are meant only for 16-Gbps speeds where FEC is optional.
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From Cisco MDS NX-OS Release 6.2(11c), FEC with Transmitter Training Signal (TTS) is supported on the Cisco MDS 9396S 16-Gbps
Multilayer Fabric Switch and Cisco MDS 9700 48-Port 16-Gbps Fibre Channel Switching Module (DS-X9448-768K9), except in Cisco
MDS NX-OS Release 6.2(13).
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From Cisco MDS NX-OS Release 8.2(1), FEC with TTS feature is supported in Simple Network Management Protocol (SNMP) and Device
Manager (DM). This feature is not supported in Cisco MDS NX-OS Release 8.1(1) or earlier.
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From Cisco MDS NX-OS Release 8.4(1), FEC admin state has changed from up or down to on or off respectively.
To configure FEC on an interface operating at 16-Gbps fixed speed, perform these steps: