IPMI on localhost

Fred Skrotzki fskrotzki at textwise.com
Wed Mar 21 13:06:42 CST 2007

Reason it does not work is simple if you think about it.  The BMC nic and the Eth0 Nic are wired together so that they each use the same transmit pair going out and the same receive pair coming in.  So the BMC can't receive what the Eth0 Nic is transmitting.  A switch down the line knows that both devices are on the same port so will NOT re-transmit the information as that would be bad normally.

-----Original Message-----
From: linux-poweredge-bounces at dell.com [mailto:linux-poweredge-bounces at dell.com] On Behalf Of Kilian CAVALOTTI
Sent: Wednesday, March 21, 2007 12:56 PM
To: linux-poweredge at dell.com
Subject: Re: IPMI on localhost

On Wednesday 21 March 2007 09:44:55 am Jesús M. Navarro wrote:
> Hi, Kilian:
> El Miércoles, 21 de Marzo de 2007 17:32, Kilian CAVALOTTI escribió:
> > Hi all,
> >
> > I have a couple PE1950 for which I configured BMCs for IPMI access.
> > Everything works perfectly when I try to access hostA's BMC from 
> > hostB. But I cannot access hostA's BMC from hostA itself.
> That's true, you can't access BMCs from itself using the LAN protocol. 
> Just try to connect without -l option.

Indeed, it works, thank you.

But I'm very curious to know why the LAN protocol doesn't work in this case. Since the BMC and the OS's network interface have two different MAC addresses, they should be considered by the switch as two different network devices, right? 

So an IPMI request issued from the OS network interface (macA) to the BMC
(macB) should be sent to the switch, which knows that macA and macB are on the same port (I checked that), so it should forward the IPMI packets back to the the same port they're coming from, where the BMC should catch them, since they're bound for macB, shouldn't it?

I'm probably missing something, but I don't see what.


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