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Fibre Channel (SAN)

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Occasional Contributor
Posts: 10
Registered: ‎07-11-2018
Accepted Solution

"Loss is above tolerable limit"

I performed a D-Port test on the ISL ports between our 6520s and on one of the ports I got the following result from portdporttest --show:

 

Roundtrip link latency: 1322 nano-seconds
Estimated cable distance: 101 meters
Buffers required: 1 (for 2112 byte frames at 16Gbps speed)
Egress power: Tx: 0.6 dBm, Rx: -2.7 dBm, Diff: 3.3 dBm (Loss is above tolerable limit)
Ingress power: Rx: -0.4 dBm, Tx: 0.0 dBm, Diff: 0.4 dBm (Loss is within tolerable limit)

 

What does "above tolerable limit" mean in this context? I don't get any errors on the port, so is some sort of action required or not?

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Contributor
Posts: 70
Registered: ‎01-19-2018

Re: "Loss is above tolerable limit"

Rx power = -2.7 looks good to me, but D-Port thinks that your link is a little dirty. Do you have any patch panels along the way or is it just straight SFP-cable-SFP connection? Anyway, you might need to clean it a little bit to improve the results. Sometimes even re-seating the cable into the SFP (and/or another connections) is already enough.

Occasional Contributor
Posts: 10
Registered: ‎07-11-2018

Re: "Loss is above tolerable limit"

The connection is something like SFP-cable-connector-cable-panel-cable-panel-cable-connector-cable-SFP. So I take it in this case no action is required?
Contributor
Posts: 70
Registered: ‎01-19-2018

Re: "Loss is above tolerable limit"

Well, yes. Rx down to -4 dBm should be OK. BTW, did you try doing D-Port test from the opposite side? It might give different results.

Occasional Contributor
Posts: 10
Registered: ‎07-11-2018

Re: "Loss is above tolerable limit"

Yes, all my test results were identical from both sides.

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