topic Re: HP switch 2600 serial port speed-duplex configuration in Switches, Hubs, and Modems

HP switch 2600 serial port speed-duplex configuration

June Hu — Fri, 09 Jan 2009 21:26:43 GMT

Hi, HP switch expert,

We are supporting Patriot Coal company network. We see several HP switches 2626, 2524 and 2650 having 10/half and 100/half links betweens. We changed the speed-duplex to 100/full but lost the switch connection immediately. Need to reboot the switch to gain network connection. Bu reading switch guideline and got feeling that any hp switch port is defaulted to auto. Other end has to be auto setting. Otherwise, the switch port only can sense 10/half and 100/half. Is this true? How can I configure a switch port to 100/full?

"Because the Series 2600 Switches behave in this way (in compliance with
the IEEE 802.3 standard), if a device connected to the switch has a fixed
configuration at full duplex, the device will not connect correctly to the
switch. The result will be high error rates and very inefficient communications
between the switch and the device.
Ensure all devices connected to the Series 2600 Switches are configured
to auto negotiate, or are configured to connect at half duplex"

Thank you,

June Hu

Re: HP switch 2600 serial port speed-duplex configuration

rick jones — Sat, 10 Jan 2009 01:07:02 GMT

Attached is some boilerplate text in support of making sure everything is set to AutoNeg - on both sides - switch and host.

Re: HP switch 2600 serial port speed-duplex configuration

Pieter 't Hart — Tue, 13 Jan 2009 12:33:16 GMT

configuring speed/duplex manulally will temporarily bring down the link.
be sure to configure the remote switch first for 100FD then the local switch.
link state should come up after some time.

I haven't checked any doc's on these switches but this will probably also disable mdi/mdix auto detection on switches that support this!!!
so you be sure to use a cross-cable for the connection.

Re: HP switch 2600 serial port speed-duplex configuration

June Hu — Wed, 14 Jan 2009 16:49:05 GMT

thank you, Rick and Pieter. I could not open Rick Jones's file. Pieter, if you have time, please check the switch doc to give me clear definition. Thank you!

June Hu

Re: HP switch 2600 serial port speed-duplex configuration

rick jones — Wed, 14 Jan 2009 17:57:56 GMT

How 100Base-T Autoneg is supposed to work:

When both sides of the link are set to autoneg, they will "negotiate"
the duplex setting and select full-duplex if both sides can do
full-duplex.

If one side is hardcoded and not using autoneg, the autoneg process
will "fail" and the side trying to autoneg is required by spec to use
half-duplex mode.

If one side is using half-duplex, and the other is using full-duplex,
sorrow and woe is the usual result.

So, the following table shows what will happen given various settings
on each side:

Auto Half Full

Auto Happiness Lucky Sorrow

Half Lucky Happiness Sorrow

Full Sorrow Sorrow Happiness

Happiness means that there is a good shot of everything going well.
Lucky means that things will likely go well, but not because you did
anything correctly :) Sorrow means that there _will_ be a duplex
mis-match.

When there is a duplex mismatch, on the side running half-duplex you
will see various errors and probably a number of _LATE_ collisions
("normal" collisions don't count here). On the side running
full-duplex you will see things like FCS errors. Note that those
errors are not necessarily conclusive, they are simply indicators.

Further, it is important to keep in mind that a "clean" ping (or the
like - eg "linkloop" or default netperf TCP_RR) test result is
inconclusive here - a duplex mismatch causes lost traffic _only_ when
both sides of the link try to speak at the same time. A typical ping
test, being synchronous, one at a time request/response, never tries
to have both sides talking at the same time.

Finally, when/if you migrate to 1000Base-T, everything has to be set
to auto-neg anyway.