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

Chuck Anderson cra at WPI.EDU
Fri Mar 26 22:09:22 UTC 2010


Anyone have suggestions on Ethernet LAN loop-prevention?  With the 
advent of Auto MDI/MDI-X ports on switches, it seems way too easy to 
accidentally or maliciously create loops between network jacks.  We 
have bored or inattentive people plugging in patch cords between 
adjacent network jacks.  STP for loop-prevention isn't working so well 
for us.

STP "edge" or "portfast" or "faststart" modes are required for 
end-station ports (with normal STP, DHCP often times out after 30+ 
seconds it takes to go into Forwarding state).  Since the "edge" STP 
mode goes into Forwarding state immediately, there is a period when 
loops will form, causing havok with upstream gear until STP blocks the 
port (if it ever does see below).

"Desktop" switches.  You know, those 4 or 5 port Gigabit Ethernet 
switches.  Apparently, many of them don't do any kind of STP at all.  
Recommendations on ones that do STP?

RSTP: is it any better than traditional STP in regards to "edge" ports 
and blocking before a loop gets out of hand?  Or perhaps blocking for 
5-10 seconds before going into Forwarding state, hopefully preventing 
loops before they happen but also allowing DHCP clients to get an 
address without timeouts?  Recommendations on "Desktop" switches that 
do RSTP?

Thanks for your suggestions/discussion.

-- 
- Chuck (354 Days until IPv4 depletion: http://ipv4depletion.com/)




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