[prev in list] [next in list] [prev in thread] [next in thread] 

List:       cisco-nsp
Subject:    Re: [c-nsp] Nexus OTV Question
From:       Martin Clifton <Martin.Clifton () vu ! edu ! au>
Date:       2011-02-28 10:50:27
Message-ID: C991C201.143B3%martin.clifton () vu ! edu ! au
[Download RAW message or body]

Thanks Lincoln,

The problem isn't associated with a single mac-address moving between
ports - at least I don't think so. Everything seems to be behaving as
expected - except for the "sh otv route" table.

For clarity, I configured only a couple of vlans over OTV.  The otv route
table quickly stabilises and can be reconciled against the originating
device.   Then, a new mac-address appears or disappears.  What then
happens is that the uptime for all pre-existing mac-addresses resets to
zero.  This is not what I would expect - I would have expected the uptimes
for the pre-existing mac-addresses to continue to increment.

Then, as I add vlans (100 or so), the number of mac-addresses increases
dramatically, and of course the probability of a change to the table
increases.  Consequently the frequency at which all of the uptimes reset
to zero increases.  This then gives the impression that the system is
quite unstable - which I don't believe it is.

Regards, Martin

---------------------------------
Martin Clifton
ITS - Networks and Computing
Victoria University
Melbourne, Australia

Phone: 03 9919 4579
---------------------------------




On 28/02/11 5:31 PM, "Lincoln Dale" <ltd@cisco.com> wrote:

> hi Martin,
> 
> On 28/02/2011, at 10:16 AM, Martin Clifton wrote:
> > I have a concern about the table that is displayed when you enter the
> > command "sh otv route".   This table shows entries for "site" (ie local)
> > and "overlay" (ie other DC)  mac addresses.    The issue is with the
> > "Uptime" data.  For the overlay addresses this will randomly reset to
> > zero and all addresses will reset to zero at the one time.   The
> > frequency of this reset seems to be a function of the number of vlans ie
> > the more vlans I add to the overlay, the more often the value resets.
> > With 100 or more vlans the value may build up to a minute or two but
> > will often only get to a few seconds before resetting.
> 
> i would not expect the "uptime" in "show otv route" to be resetting.
> that, to me, indicates that the MAC address(es) are moving/oscillating
> between ports on the originating device.
> with OTV we still do hardware-based MAC learning for L2 switching but
> whenever a MAC address is learnt or moves that is picked up by
> control-plane and advertised accordingly.
> 
> for one of those mac addresses, suggest you look into whether it is in
> fact moving - and more importantly - why.  it could be a misconfiguration
> (like Port Channel "mode on" on one device and no Port Channel defined on
> the other end.
> it could be misconfigured hosts - set up with NIC teaming or Link
> Aggregation incorrectly.
> it could be unstable L2 at one side.
> t could be a loop.  (but i'd expect that to be having more noticable
> impacts on the network :) ).
> 
> pick one of the N7Ks where you see the change originating from and do a
> few "show hardware mac address-table <slot-number> | grep <macaddr>" and
> see if its moving.  that shows the h/w mac table.  you may also see the
> same moving of mac addresses in "show mac address-table" but the h/w one
> will show updates sooner.
> 
> 
> cheers,
> 
> lincoln.

This email, including any attachment, is intended solely for the use of the intended \
recipient. It is confidential and may contain personal information or be subject to \
legal professional privilege. If you are not the intended recipient any use, \
disclosure, reproduction or storage of it is unauthorised. If you have received this \
email in error, please advise the sender via return email and delete it from your \
system immediately. Victoria University does not warrant that this email is free from \
viruses or defects and accepts no liability for any damage caused by such viruses or \
defects.

_______________________________________________
cisco-nsp mailing list  cisco-nsp@puck.nether.net
https://puck.nether.net/mailman/listinfo/cisco-nsp
archive at http://puck.nether.net/pipermail/cisco-nsp/


[prev in list] [next in list] [prev in thread] [next in thread]