Bizarre serial console redirection behavior with PE1950/2950 III BMC

[Alexander Dupuy]

A month ago, I asked:
> With console redirection set to COM2, but redirection after boot 
> disabled, and ISOLINUX / GRUB / Linux kernel configured to use the 
> COM2 serial port (ttyS1), the Linux system and its boot helpers are 
> getting tons of bogus data coming into the serial port - unless an SOL 
> session has been established.
>
> Running cat /dev/ttyS1 once Linux is up and running (this required 
> disabling the serial port for ISOLINUX and GRUB), I am seeing lines 
> like the following:
>
> [SYS]
>
> [ERR D5]
>
> which make me think that somehow the BMC is in terminal mode and 
> talking to the Linux kernel (RHEL 5.1) and boot utilities over the 
> COM2 serial interface (and these messages are responses to the login 
> or other prompts, and/or kernel echoing of input characters).  ... 
> Once an SOL session is established the chatter on the serial interface 
> goes away.
>
> Has anyone seen any strange behavior like this, or have any ideas 
> about how to disable it? (I don't think this is a hardware problem as 
> I'm seeing it on all the new systems).  Any replies greatly appreciated.
>

I didn't get any replies, but seem to have solved the problem myself 
with the following command:

# syscfg serialchannelaccess --ipmioverserial=disable

which disables the IPMI over serial support in the BMC (I am only using 
the LAN access, and running serial console with serial-over-LAN).  This 
lends some credence to the theory that when the serial-over-LAN IPMI 
access was not active, that the IPMI serial support was somehow 
connected to the virtual COM2 port in a way that the BMC and the host 
CPU were chattering away at each other.

@alex

-- 
mailto:alex.dupuy at mac.com