Thanks Priscilla, I understand what you mean now. That's why those ports which directly connected to PCs need to configured as spanning-tree portfast to minimize the STP state change.
>From: "Priscilla Oppenheimer" >Reply-To: "Priscilla Oppenheimer" >To: [EMAIL PROTECTED] >Subject: RE: why this caused whole network hang? [7:60090] >Date: Fri, 3 Jan 2003 04:01:41 GMT > >Kenny Smith wrote: > > > > Hi.. Priscilla and Dear all, > > > > Thanks for your explaination and sorry for my ignorance. But I > > don't > > understand one part about "it doesn't hear BPDUs from the other > > side. This > > can result in it setting one of its ports into fowarding mode > > when it > > souldn't." But my switch has only one connection to my > > backbone switch. So > > I don't understand how it will creat STP loop? > >Well maybe it wasn't a loop. But a duplex mismatch problem will cause BPDUs >to flow inconsistently which could cause STP to reconverge incessantly or >other problems. I wasn't there and I don't know your topology, so I can't >say for sure what happened. > >Priscilla > > > > > > >From: "Priscilla Oppenheimer" > > >Reply-To: "Priscilla Oppenheimer" > > >To: [EMAIL PROTECTED] > > >Subject: RE: why this caused whole network hang? [7:60090] > > >Date: Thu, 2 Jan 2003 21:44:06 GMT > > > > > >A duplex mismatch problem somewhere in the network can indeed > > cause > > >problems > > >for STP. It's an example of the infamous unidirectional link > > problem, which > > >is also known as the one-way connectivity failure. > > > > > >The side that is using full-duplex can send OK because it > > ignores the fact > > >that the other side is sending at the same time. The side that > > is using > > >half-duplex gets excessive collisions and gets so busy > > handling those that > > >it can't send or receive frames reliably. So it doesn't hear > > BPDUs from the > > >other side. This can result in it setting one of its ports > > into fowarding > > >mode when it souldn't. > > > > > >Cisco has a feature to avoid unidirectional link problems. Try > > looking up > > >their Unidirectional Link Detection protocol, although the > > real fix in this > > >situation isn't to use the protocol, but, rather to fix the > > duplex problem, > > >as you know. > > > > > >Priscilla > > > > > > > > >Kenny Smith wrote: > > > > > > > > Hi.. I have one of my 2900 switch connected to my backbone > > > > switch(5500). A > > > > few day ago, I found that the switch to switch connection > > has > > > > duplex > > > > mismatch error. The 2900 sw interface was set to 100 full > > dpx. > > > > But the 5505 > > > > sw interface was set to auto neg, but they fail to negotiate > > > > properly. > > > > Therefore, I tried to set the 5505 sw interface to 100 full > > > > dx. But > > > > immediately after I set, the whole company network hang. All > > > > users lost > > > > connection for more than 10 minutes. > > > > > > > > I really can't understand why?? The 2900 sw has only one > > > > connection to the > > > > 5505 sw and both interface set to portfast (faststart) > > > > disable. I think it > > > > is related to spanning-tree but why spanning-tree loop will > > > > happen in this > > > > case. Can one explain to me. > > > > > > > > Thanks a lot > > > > > > > > > > > > > > _________________________________________________________________ > > > > Protect your PC - get McAfee.com VirusScan Online > > > > http://clinic.mcafee.com/clinic/ibuy/campaign.asp?cid=3963 > > _________________________________________________________________ > > MSN 8 with e-mail virus protection service: 2 months FREE* > > http://join.msn.com/?page=features/virus _________________________________________________________________ STOP MORE SPAM with the new MSN 8 and get 2 months FREE* http://join.msn.com/?page=features/junkmail Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=60188&t=60090 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
