X350-24t strange behavior with speed ports

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Hello, all!

have X350-48t with connected lap-top.
When port speed is auto - all normal
When configure port as 100 duplex full - speed is very decrease

Try with SpeedTest, below results:
autonegotiate as 100 full - speedtest=95Mbps 
configure as 100 full - speedtest=20-25Mbps

Does anybody has same problem?

Try with EXOS 15.3.4.6 patch 1-14 and EXOS 15.3.1.4 patch 1-47

Thank you!
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Alexandr P, Embassador

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Posted 2 years ago

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Erik Auerswald, Embassador

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Hello Alexandr,

did you re-configure the laptop to use 100/full duplex before changing the switch settings?

Your test results indicate that the laptop is configured to use auto-negotiation, which works fine. If you turn off auto-negotiation on the switch, but leave it enabled on the laptop, the laptop will use 100/half duplex, but the switch will use 100/full duplex. This results in transmission errors and thus degraded performance.

Br,
Erik
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Jarek

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Hi Alexandr,

probably your laptop has a sync problem and his interface is synced as 100 half duplex.
Set laptop card to 100 full duplex and check again.

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Jarek
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Alexandr P, Embassador

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When configure lap-top with 100Mbps full duplex - all work fine.
BUT
Trying Linksys SPS224G4 - in the same situation speed don't decrease, put back Extreme - speed is dercease.

Thank you!
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Jarek

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Probably Linksys didn't disable autoneg. even if you have disabled it in configuration.
( sorry SOHO is cheap :) )

I know that we are on Extreme forum, but bellow a link that I think have a good explanation for that issue and what we should expect when we change speed and duplex.
(I understand if moderators  delete this link )

http://www.cisco.com/c/en/us/support/docs/switches/catalyst-6500-series-switches/17053-46.html

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Jarek

PS.  (to Extreme ) Maybe you can write similar description and add it to GTAC or documentation ?
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Erik Auerswald, Embassador

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TL;DR version: speed is auto-detected even without auto-negotiation, duplex is not auto-detected without auto-negotiation. Thus the side with auto-negotiation uses the correct speed, but uses to half-duplex operation. The other side uses the hard-coded values.

Back in the 1990s, when auto-negotiation did not work properly with some vendor combinations, access ports in some networks were configured for 100/half-duplex to work with both auto-negotiating NICs and those with the correct fixed configuration.

Br,
Erik
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Jarek

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We see even today some issues with cheap SOHO routers that customers have.
They work with simple unmanaged switch, but when you connect them to Extreme or other vendor box,  then you can have a lot of fun...

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Jarek
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Erik Auerswald, Embassador

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Hello Alexandr,

I cannot tell you what the Linksys switch does, but you can have different results because of different configuration methods:

  1. Link speed can be configured by disabling auto-negotiation and specifying speed and duplex.
  2. Link speed can be configured by enabling auto-negotiation but restricting the advertised values for speed and duplex settings.
You can both of these methods on both EOS and EXOS based switches. I do not know what the Linksys switch does.

The easiest way to check what a device does regarding auto-negotiation is to connect it to an EOS switch and use the command "show port advertise". This will show you the local and the remote settings.

Br,
Erik