[124232] in North American Network Operators' Group
RE: Auto MDI/MDI-X + conference rooms + bored == loop
daemon@ATHENA.MIT.EDU (Matthew Huff)
Fri Mar 26 18:21:46 2010
From: Matthew Huff <mhuff@ox.com>
To: 'Chuck Anderson' <cra@WPI.EDU>, "'nanog@nanog.org'" <nanog@nanog.org>
Date: Fri, 26 Mar 2010 18:21:08 -0400
In-Reply-To: <20100326220922.GH12189@angus.ind.WPI.EDU>
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
Bpduguard if running cisco.
=20
set all the switch ports to bpduguard or enable it globally
-----Original Message-----
From: Chuck Anderson [mailto:cra@WPI.EDU]=20
Sent: Friday, March 26, 2010 6:09 PM
To: nanog@nanog.org
Subject: Auto MDI/MDI-X + conference rooms + bored =3D=3D loop
Anyone have suggestions on Ethernet LAN loop-prevention? With the=20
advent of Auto MDI/MDI-X ports on switches, it seems way too easy to=20
accidentally or maliciously create loops between network jacks. We=20
have bored or inattentive people plugging in patch cords between=20
adjacent network jacks. STP for loop-prevention isn't working so well=20
for us.
STP "edge" or "portfast" or "faststart" modes are required for=20
end-station ports (with normal STP, DHCP often times out after 30+=20
seconds it takes to go into Forwarding state). Since the "edge" STP=20
mode goes into Forwarding state immediately, there is a period when=20
loops will form, causing havok with upstream gear until STP blocks the=20
port (if it ever does see below).
"Desktop" switches. You know, those 4 or 5 port Gigabit Ethernet=20
switches. Apparently, many of them don't do any kind of STP at all. =20
Recommendations on ones that do STP?
RSTP: is it any better than traditional STP in regards to "edge" ports=20
and blocking before a loop gets out of hand? Or perhaps blocking for=20
5-10 seconds before going into Forwarding state, hopefully preventing=20
loops before they happen but also allowing DHCP clients to get an=20
address without timeouts? Recommendations on "Desktop" switches that=20
do RSTP?
Thanks for your suggestions/discussion.
--=20
- Chuck (354 Days until IPv4 depletion: http://ipv4depletion.com/)
