Servers unable to connect to their own DRAC

Fred Skrotzki fskrotzki at textwise.com
Tue Sep 9 13:31:23 CDT 2008


As for why it can't work when using the same nic port for both.  It's
simple when you think about it.  The port has a transmit pair and a
receive pair.  The BMC and regular nic transmits are tied together and
so are the receives, without a switch in-between so since both use the
same transmit pair to send (yes it is a bit over simplified as there is
a traffic signal gate someplace so that both don't step on each) other.
Thus how can the NIC hear the BMC and the BMC hear the NIC.  And a
switch is a smart device that knows that any requests coming from one of
it's ports should not be re-transmitted back, only to other ports
otherwise there is other issues.

Now on the newer servers both nic's and the BMC are all tied into one
chip so I'm sure that has something to do with it.

For a simpler solution why not load the ipmi drivers and ipmitools and
talk directly.  That's how each machine we have can query itself.  The
command ipmitool -I open .... Will tell the tool to use the driver
interface instead of the network lan.

-----Original Message-----
From: linux-poweredge-bounces at dell.com
[mailto:linux-poweredge-bounces at dell.com] On Behalf Of Matthias Saou
Sent: Tuesday, September 09, 2008 9:55 AM
To: linux-poweredge at lists.us.dell.com
Subject: Servers unable to connect to their own DRAC

Hi,

I'm pretty sure many on this list are familiar with this limitation :
Servers can't seem to connect to their own BMC or DRAC IP address.
I'm still not sure what the reason for this is, but so be it.

What I really don't understand, though, is that when using a DRAC with
its dedicated RJ45 port and not shared on the server's NIC1, things
still don't work.

Since the DRAC is supposed to be physically separate from the rest of
the server, I really don't understand how this setup can't work. I've
tried forcing the DRAC MAC address to the NIC1 interface with no luck.

Does anyone know of a fix or workaround? Or the reason for all this?

The problem here is not to get the serial console or reboot the server,
it's for IPMI monitoring from the server itself.

Matthias

--
Clean custom Red Hat Linux rpm packages : http://freshrpms.net/ Fedora
release 9 (Sulphur) - Linux kernel 2.6.25.11-97.fc9.x86_64 Load : 0.12
0.20 0.40

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