Hi Marko Can you expand if possible on why bpdu filter would cause temp loops? Are you saying that the bpdu is stripped from an Ethernet frame when this happens?
This may be a stupid question but when we filter bpdu's then I presume this doesn't include the whole 802.3 frame, as I understand it a bpdu is added to the payload of the 802.3 Ethernet frame and is 35 bytes in size or am I going completely off the scales here and have I got knowledge gaps... Or are we talking STP BPDU's for control only... To picture my understanding: http://www.google.co.uk/search?q=bpdu+where+in+ethernet+frame&oe=UTF-8&hl=en&client=safari&um=1&ie=UTF-8&tbm=isch&source=og&sa=N&tab=wi&ei=RNRdUaedD4iL4AT6roCwAw&biw=768&bih=928&sei=SNRdUeKnIei00QW54YHoAQ#biv=i%7C4%3Bd%7CgoRoh1hn961EyM%3A -- BR Tony Sent from my iPad On 4 Apr 2013, at 19:49, Marko Milivojevic <[email protected]> wrote: > That's a very valid question and one that I get asked often :-) > > Generally speaking, you are right - as soon as PortFast receives a BPDU it > will be disabled and the port transitioned into the appropriate state > (remain forwarding or end up being blocked/discarding). > > However… > > There is that brief period of time before a BPDU has been received during > which, depending on the amount of the traffic in your network, bad things > could happen due to the loop that was briefly formed. > > I personally think that warning message is misplaced. It should appear when > you configure BPDU Filter on the interface and not PortFast, but that's > just me :-) > > -- > Marko Milivojevic - CCIE #18427 (SP R&S) > Senior CCIE Instructor / Managing Partner - IPexpert > > > On Thu, Apr 4, 2013 at 2:39 AM, Quentin Huberty > <[email protected]>wrote: > >> Hi all,**** >> >> ** ** >> >> Is anybody know why the message below appears when portfast is activated ? >> **** >> >> ** ** >> >> %Warning: this command enables portfast by default on all interfaces. You* >> *** >> >> should now disable portfast explicitly on switched ports leading to hubs, >> **** >> >> switches and bridges as they may create temporary bridging loops.**** >> >> ** ** >> >> I mean, I tested and each time I received BPDU on interface where portfast >> is enabled (per interface or globally) the portfast is automatically >> disabled and STP run...**** >> >> ** ** >> >> How a loop can be created ? >> > _______________________________________________ > For more information regarding industry leading CCIE Lab training, please > visit www.ipexpert.com > > Are you a CCNP or CCIE and looking for a job? Check out > www.PlatinumPlacement.com > > http://onlinestudylist.com/mailman/listinfo/ccie_rs _______________________________________________ For more information regarding industry leading CCIE Lab training, please visit www.ipexpert.com Are you a CCNP or CCIE and looking for a job? Check out www.PlatinumPlacement.com http://onlinestudylist.com/mailman/listinfo/ccie_rs
