Re: Auto MDI/MDI-X + conference rooms + bored == loop

[Chuck Anderson <cra () WPI EDU>]

On Sat, Mar 27, 2010 at 02:11:32AM -0700, Owen DeLong wrote:
> Sounds like you forgot to configure the "Root is that-way ->" sanity
> check on your switches.  Make sure that Root bridge can't be
> determined to be in a direction other than "upstream" will help
> a lot with this.

No STP in the core, only on the managed edges.

> > So basically, the problem is the core switches implement a proprietary
> > loop-prevention protocol that sends "beacon" frames out every 500ms,
> > and if a certain number of these special frames come back (exceeds
> > threshold) it shuts down the port.  Even with a 10:1 ratio of
>
> That's Icky... Can you replace that with traditional spanning tree?
> It's just too sensitive for a deployment of any real size.

STP is eliminated by vendor's design recommendations.  Active/active 
split LAG across two core boxes.  But yes, I agree that this design is 
proving--lacking.

> > The good news is that this core is being replaced soon, hopefully with
> > gear that will be able to implement a service-provider-like design
> > with per-port VLAN separation as was suggested in this thread.  But it
> > surprises me that low-end switch vendors (like NetGear) still put out
> > crap that doesn't do STP, especially when the switch does Auto
> > MDI/MDI-X, which is just asking for trouble.
> Usually people don't use Netgear cheap switches in environments with
> more than a desktop worth of topology.

We don't generally put them in, users do.  There are a few cases where 
we have a dearth of cable or conduit space and needed something small 
and quiet to put there.  Hence my question about better switches to 
use in those scenarios.

> > Anyone know if Auto MDI/MDI-X is inherent or required in 1000Base-T?
> > It would be nice if I could shut it off.
> Yes, it is. (This is actually a good thing in everyone else's  
> environment).

It's easy to claim that no one else but me has this problem.  
Designing a "dekstop" switch that makes it easy to create accidental 
loops, but then has no loop-prevention mechanism seems irresponsible 
to me...