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Server Speed/Duplex Settings

Bergin
Advisor

Server Speed/Duplex Settings

All,

Anyone have a quick link to a best practices document (HP or otherwise) on how servers should be connected to a switch.

Should switch be Auto or Forced 100 Full and if so then should desktop/server be set to the opposite or the same.

I think if one side is 100 Full then otherside should match, if both are set to Auto then sometime switch will auto negotiate at a first available speed (which may or may not be the fastest available).

Thanks,

Rob
5 REPLIES
Bergin
Advisor

Re: Server Speed/Duplex Settings

I found some articles on the topic:

http://forums1.itrc.hp.com/service/forums/questionanswer.do?threadId=1031705

"Most of the time it is recommended that you set both the nic and the switch port to auto/auto for operations a 1Gbps. However, I have found that some switch/nic combinations don't autonegotiate nicely. If that is the case, then start with 100/full on both sides, then try 1000/full, making sure you have an alternate way of getting into the machine in case it fails.

In general, it is best to have both sides of a connection configured the same way. Even though it seems possible, setting one side to a fixed setting and the other to autonegotiate never works right."

vs.

"You should set the card to Auto/Auto. Then check the connection speed at the switch. The server may be giving you bad information. If you are still connecting at 10/full then either your ports are set incorrectly or there may be a wiring problem.
As a general rule you should always have the latest drivers for the NIC when connecting at GB."

And I just wanted to know if there is a paper/support doc that covers it.

Thanks,

Rob
Ron Kinner
Honored Contributor

Re: Server Speed/Duplex Settings

They should always match. If you assign one side as Auto and the other as FULL you will find that the Auto side is set to HALF. That's what the specs for autonegotiate tell it to do so it has no choice.

In the old days autonegotiate wasn't always reliable and most people routinely set both sides to Full. These days the bugs are out of it and Auto seems to work nicely so I would leave both sides set to auto.

Ron
Matt Hobbs
Honored Contributor

Re: Server Speed/Duplex Settings

I couldn't agree more - leaving everything at Auto is going to cause you far less aggravation in the long run.

Fortunately with 1000Base-T, Auto negotiate is mandatory (even though you can often select 1000-Full, it's actually just advertising only that speed and duplex in its Auto negotiation bits).
rick jones
Honored Contributor

Re: Server Speed/Duplex Settings

Another voice for leaving things at auto unless and until you determine that auto is broken, unfixable, and the broken kit unreplaceable.

Attached is some boilerplate about Autoneg.
there is no rest for the wicked yet the virtuous have no pillows
Lucky Luciano
Regular Advisor

Re: Server Speed/Duplex Settings

Hi
for me for few servers it made combination of full on switch and auto on server results of having half duplex on, but it was only on DL360. Another case is that in case of teaming it was always a question of tests what will work at best. Dell's servers appears to that as "ignorants" they were pluged and it is not important if teaming set on switch or server they work fine.
For HP servers I had always to try carefully what will be the best choice.
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