Posted on November 23, 2021 9:48 pm
 |  Asked by Tim McCarthy
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My customer is using a Arista switch capable of 100G. They are using supported 100G optics on the Arista side. We have placed NetApp optics (purchased from NetApp) on the NetApp side. Using an OM4 MTP(or MPO) cable to connect. Any traffic generated results on errors on the Arista switch side and very slow performance.

(I know…I am lacking some details like switch model and EOS version, I will share when I have that. I am hoping this can be answered more genericly)

As a test, the peer-link was replaced with the Arista supported 100G optics and the same cable running to the NetApp. Data was generated and no errors were seen on the Arista switch.

What I am asking, what is Arista’s response to the “best supported” port configuration to connect with 100G (SR) optics to a NetApp controller?

I see this all available:

  100full        Disable autoneg and force 100 Mbps/full duplex operation
  100g           Disable autoneg and force 100 Gbps/full duplex operation over 4 or 10 lanes
  100g-2         Disable autoneg and force 100 Gbps/full duplex operation over 2 lanes
  100g-4         Disable autoneg and force 100 Gbps/full duplex operation over 4 lanes

Which one setting should used? We have tried some of these and they seem to connect, just generate errors.
Any ideas? Thanks

Posted by Kenneth Finnegan
Answered on November 24, 2021 6:44 pm

Howdy Tim, I'm guessing that you're using a 100G-SR4 optic in a regular QSFP28 Ethernet port.

The 100g and 100g-4 speeds are both aliases for the same thing, which is 100G implemented as 4 lanes of 25G, which is what you want for a 100G-SR4 optic.

The 100g-2 configuration is only relevant for 200G QSFP56 or 400G QSFP-DD/OSFP ports, where 100G is implemented as 2 lanes of 50G each. 100full is.... well... 100Mbps, so three orders of magnitude slower than what you want.

100G-SR4 optics should default to being a 100G interface, so I'm not convinced you even need a speed forced configuration on your interface, but this may depend on some specifics of the Arista platform you're running on.

If you were seeing errors on the link, but they went away when you replaced the NetApp side optic, this sounds like a problem with the original NetApp optic. All 100G-SR4 optics can interoperate on the fiber side, so there isn't anything special about the light coming out of an Arista SR4 optic vs anyone else's.

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