Mailing List Archive: FEC on 25G-LR links between Juniper and Arista

Hi,

we've run in some weird issue with 25G links and FEC between Juniper
QFX5120 and Arista.

We have functioning links using 25G-SR optics and FEC108
(Reed-Solomon) error correction. On Arista thats default, on the QFX
we use

set interfaces et-0/0/46 gigether-options fec fec108

This works.

Trying the same on another switch with 25G-LR optics doesn't work.

The only way to get the interface up is to either

a) disable FEC on Arista
or
b) setting both Arista and Juniper to the (inferior) FEC74 (Fire-Code).

Any idea why that is? Does anyone here have working 25G-LR links using
Reed-Solomon FEC between Arista and Juniper? Also tried FEC91 on
the Juniper side without success.

Best Regards

Sebastian

--
'Are you Death?' ... IT'S THE SCYTHE, ISN'T IT? PEOPLE ALWAYS NOTICE THE SCYTHE.
-- Terry Pratchett, The Fifth Elephant
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* Sebastian Wiesinger via juniper-nsp <juniper-nsp@puck.nether.net> [2023-12-06 12:55]:
> Hi,
>
> we've run in some weird issue with 25G links and FEC between Juniper
> QFX5120 and Arista.
>
> We have functioning links using 25G-SR optics and FEC108
> (Reed-Solomon) error correction. On Arista thats default, on the QFX
> we use
>
> set interfaces et-0/0/46 gigether-options fec fec108
>
>
> This works.
>
> Trying the same on another switch with 25G-LR optics doesn't work.

To answer my own question: Found out that FEC108 for JunOS with 25G-LR
optics was implemented from 23.1 onwards, currently running on
23.2R1-S1 with FEC108 enabled on JunOS and default config on Arista.

Best Regards

Sebastian

--
'Are you Death?' ... IT'S THE SCYTHE, ISN'T IT? PEOPLE ALWAYS NOTICE THE SCYTHE.
-- Terry Pratchett, The Fifth Elephant
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