[124254] in North American Network Operators' Group
Re: Auto MDI/MDI-X + conference rooms + bored == loop
daemon@ATHENA.MIT.EDU (Chuck Anderson)
Sat Mar 27 10:58:32 2010
Date: Sat, 27 Mar 2010 10:57:51 -0400
From: Chuck Anderson <cra@WPI.EDU>
To: "nanog@nanog.org" <nanog@nanog.org>
Mail-Followup-To: "nanog@nanog.org" <nanog@nanog.org>
In-Reply-To: <B8F9B3C8-1C7E-408F-9A10-841BEAA3E0EE@delong.com>
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
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...
