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  1.  Home
  2. MIDRANGE-L
  3. August 2017

Re: HMC to Rack communcations

Rob
The IBM guy said:
"
Use the -M switch to set do not fragment and -s to increase the size. See
if it will pass the 1412 MTU. For example:ping -M do -s 1412
"
That would make me believe that the required unfragmented packet size would
be 1412, if your ping is working thru the albion route with that MTU, why
would it break the HMC functionality? maybe the IBM guy just took 1412 out
of his hat as a number?
Also, I did say before that you need root permission to really be root in
the HMC; hscroot is NOT root, and is chrooted into a tiny box where it can
only do what IBM wants you to do. A lot of commands you usually use on a
linux box are restricted to the root user in the HMC and require IBM to
generate a time-sensitive password to use.
I concur with you in that the network must work no matter the route the
packets take. Otherwise it's not a redundant network, so either they take
down the route (maybe define that packages from the HMC cannot traverse the
network that way?) or they fix it. But let it be known that it's on their
head if someday you can't access the machines due to a failed link...

Best Regards,
Roberto

On Mon, Aug 7, 2017 at 9:11 AM, Rob Berendt <rob@xxxxxxxxx> wrote:

Where are we getting the MTU at 1412? Every where I see says it's at
1500. I can ping a 1412 MTU for quite some time with no issues. It's the
larger size that shows errors on ping.


Rob Berendt
--
IBM Certified System Administrator - IBM i 6.1
Group Dekko
Dept 1600
Mail to: 2505 Dekko Drive
Garrett, IN 46738
Ship to: Dock 108
6928N 400E
Kendallville, IN 46755
http://www.dekko.com





From: Roberto José Etcheverry Romero <yggdrasil.raiker@xxxxxxxxx>
To: Midrange Systems Technical Discussion <midrange-l@xxxxxxxxxxxx>
Date: 08/04/2017 05:06 PM
Subject: Re: HMC to Rack communcations
Sent by: "MIDRANGE-L" <midrange-l-bounces@xxxxxxxxxxxx>



You don't have ROOT access to the HMC until IBM tells you the
time-generated password. So I don't think you can change it unless support
wants you to change it. You must have some ADSL or similar encapsulated
links to not be able to use MTU=1412, then again they said that HMC needs
MTU = 1412 OR a network that allows the points to negotiate the MTU thru
ICMP. Have you talked to the network guys about this?
There are reasons to disallow packet fragmentation, it's not something you
ask for unless you need it.
Best of luck!

On Fri, Aug 4, 2017 at 5:34 PM, Kevin Bucknum <Kevin@xxxxxxxxxxxxxxxxxxx>
wrote:

Maybe it's not in your path? /usr/bin/traceroute rack1





Kevin Bucknum
Senior Programmer Analyst
MEDDATA/MEDTRON
Tel: 985-893-2550

-----Original Message-----
From: MIDRANGE-L [mailto:midrange-l-bounces@xxxxxxxxxxxx] On Behalf
Of Rob Berendt
Sent: Friday, August 4, 2017 3:31 PM
To: Midrange Systems Technical Discussion
Subject: RE: HMC to Rack communcations

login as: hscroot
hscroot@hmc02's password:

hscroot@HMC02:~> traceroute rack1
bash: traceroute: command not found


Rob Berendt
--
IBM Certified System Administrator - IBM i 6.1 Group Dekko Dept 1600
Mail
to: 2505 Dekko Drive
Garrett, IN 46738
Ship to: Dock 108
6928N 400E
Kendallville, IN 46755
http://www.dekko.com





From: "Kevin Bucknum" <Kevin@xxxxxxxxxxxxxxxxxxx>
To: "Midrange Systems Technical Discussion"
<midrange-l@xxxxxxxxxxxx>
Date: 08/04/2017 04:29 PM
Subject: RE: HMC to Rack communcations
Sent by: "MIDRANGE-L" <midrange-l-bounces@xxxxxxxxxxxx>



Traceroute works, and you should be able to set the mtu with ifconfig,
but I have never tried it.




Kevin Bucknum
Senior Programmer Analyst
MEDDATA/MEDTRON
Tel: 985-893-2550

-----Original Message-----
From: MIDRANGE-L [mailto:midrange-l-bounces@xxxxxxxxxxxx] On
Behalf
Of Rob Berendt
Sent: Friday, August 4, 2017 3:23 PM
To: Midrange Systems Technical Discussion
Subject: Re: HMC to Rack communcations

Is there a way to lower the MTU size from 1500? I looked here and
do
not
see any such thing.

https://www.ibm.com/support/knowledgecenter/en/POWER8/p8edm/chh
mc.html

Does HMC have a traceroute command?



Rob Berendt
--
IBM Certified System Administrator - IBM i 6.1 Group Dekko Dept 1600
Mail
to: 2505 Dekko Drive
Garrett, IN 46738
Ship to: Dock 108
6928N 400E
Kendallville, IN 46755
http://www.dekko.com

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