bugtraq - Re: DoS of LAN via D-Link switches

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Message-ID: <9c177ed4b5e7c204902fae209bb6860d@thermeon.com>
Date: Wed, 30 Mar 2005 16:19:36 -0600
From: Scott Nelson <sbn@...rmeon.com>
To: Neil Watson <bugtraq@...son-wilson.ca>
Cc: bugtraq@...urityfocus.com
Subject: Re: DoS of LAN via D-Link switches


Neil Watson wrote:
> From: Frank Bures [mailto:lisfrank@...m.toronto.edu]
> Sent: Tuesday, March 29, 2005 4:41 AM
>> In my opinion, a switch should be immune to this admittedly insane
>> manipulation.  Otherwise, one can DoS the entire network just
>> by shorting
>> two RJ-45 network outlets in one's office together.
>
> I believe what you are describing is officially called a bridge loop.  
> A
> bridge loop occurs when a switch, or stack of switches are plugged into
> themselves.  The result is that the switches report the same MAC 
> address
> at multiple ports.  The solution to this is called Spanning Tree
> Protocol.  STP is a set of algorithms that help switches remove
> redundant MAC entries.

And it can be particularly hard to find.  XO Communication's Irvine 
Data Center has been struggling with what they believe to be the same 
kind of problem for the last couple of days (and I've been struggling 
with connectivity).