serial over lan

Don Holmgren djholm at
Sat Feb 22 11:31:55 PST 2003

On Fri, 21 Feb 2003, Donald Becker wrote:

> On Fri, 21 Feb 2003, Dale Harris wrote:
> > Just wondering if anyone is doing anything with Serial over LAN?  I
> > heard that H.J. Lu had written some driver for linux.  I assume this is
> > something you can use to do serial console redirect.  Or at least that
> > is some of the suggestion at:
> >
> >
> This is IPMI serial port redirect.
> While it's not specifically part of IPMI 1.5, most IPMI 1.5 implementations
> include it.
> Power control and serial port redirect (BIOS setup and boot status
> monitoring) are the features that makes IPMI 1.5 really compelling
> for cluster hardware (albeit with a ugly underlying implementation).
> Combined it with serial port redirect for BIOS configuration, you can
> manage everything on the machine over the network.  Even without an OS
> or a crashed system, you can still examine the hardware and control power.
> The implementation is challenging and varies by system.  We implement it
> for customers, but right now it would be a huge amount of work to
> support it for aribitrary kernels and configurations.
> --
> Donald Becker				becker at
> Scyld Computing Corporation
> 410 Severn Ave. Suite 210		Scyld Beowulf cluster system
> Annapolis MD 21403			410-990-9993

A quick comment and a question.

The serial port redirect available on the IPMI option cards on
SuperMicro motherboards is significantly flawed, at least in the current
implementation of the firmware.  They are evidently using the BMC
processor to snoop the memory area used by the standard BIOS text
console.  This snooping is quite disruptive - all cpu activity slows
down considerably, perhaps as a result of halting the processor.  I just
did a quick experiment, and saw the time of day clock lose 15 seconds
during just 60 seconds of serial port redirection.  To notice this
effect, you have to literally use wall time, as cpu-based timings show
no change.  Also, even in the BIOS screens the tool is almost useless
because of slow performance and dropped characters.  I was hoping to
avoid wiring serial ports for BIOS access and a Linux serial console,
but have now been forced into this.  This is a pity since the ethernet
solution is essentially free, and serial multiplexers for a large
cluster are at least $50/port.

Now the question - the ability to do remote reset and power cycling in
IPMI is a great feature.  I've been doing this for several years, going
back to the old Nightshade and Lancewood motherboards with their IPMI
access over the EMP, and now via the ethernet portal specified in the
IPMI 1.5 specification.  I'm currently using a Java utility which comes
with the IPMI option card to issue the IPMI commands.  However, the
utility can't be scripted and is very cumbersome to configure.

Does anyone know of available code to do the IMPI 1.5 communications
over TCP/IP?  OpenIPMI at SourceForge doesn't seem to address this (I
may be wrong, but it seems to only handle local access to the BMC via
the most commonly implemented internal mechanism, KCS).  If not, I'll
start on an implementation soon, but I'd love to bypass this bit of

Don Holmgren

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