""Priscilla Oppenheimer"" wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > I agree with Chuck that you don't want to enable portfast on a port that > connects a switch. You could disable STP all together, as Chuck mentions, > but that is risky unless you have complete control of network equipment > installs, good documentation of your logical and physical topology, and a > good change control process. > > But you could look into Cisco's other features, such as Uplink Fast and > Backbone Fast. These speed up STP convergence time. Their proper use is > dependent on your topology, which I admit I didn't look at carefully. Hey, > my state is on fire, and I'm a little distracted! ;-)
CL: I may be misunderstanding, but I believe that Uplink Fast and Backbone Fast are appropriate for exsiting topologies where failures may occur. If a new switch is introduced into the mix, I'm not sure that these features speed up or bypass STP. CL: hhmmm..... looking through the documentation, I see a feature called Cross-stack Uplink fast which might be worth looking at. Mentions the gigastacks specifically. Use the "spanning-tree stack-port" command on the gigabit interfaces. There is mention of the introduction of a new switch in the documentation of this feature. CL: hope all is well n your neighborhood. These fires have been pretty scary to a lot of people. > > Priscilla > > Chuck's Long Road wrote: > > > > Some comments below: > > > > ""dovelet"" wrote in message > > [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > > > Hi all, > > > > > > I have a question about Cisco Catalyst 3500XL switch with > > Gigastack in > > > Spanning Tree, and I hope someone can help me. I have a > > network like this: > > > > > > [Root] > > > SW1 ----- Gigastack (1)------ SW2 > > > |----------Gigastack (2) -----x--| > > > > > > I have 2 Cat.3500XL switches and use 2 gigastack cable to > > connect them. It > > > work fine and I found that the LED on Gigastack (1) is green > > while the > > > SW2-Gigastack (2) is in amber. I assume that the port on > > SW2-Gigastack (2) > > > is spanning tree blocking. Now, I want to install one more > > Cat.3500XL > > > switch. Then I disconnect the cable SW2-Gigastack (2). > > However, I found > > that > > > the network connection between the two switches are broken > > for about > > 50sec. > > > I think it is due to spanning tree re-learning. > > > > CL: yes. this is the way spanning tree works. new links > > detected. STP runs. > > This is intentional, and is to ensure loop free topologies. > > this is alos the > > bane of network managers everywhere, for a lot of reasons. > > > > > > > > >Then I install a new Cat.3500XL (SW3) into the stack. > > > > > > [Root] > > > SW1 ----- Gigastack (1)------ SW2 > > > | > > > |----------Gigastack (2) -----SW3 > > > > > > However, I found that the network connection between SW1 and > > SW2 was > > broken > > > again for about 50 sec. The spanning tree re-learn again! > > > > CL: sounds about right. > > > > > > > > > > My questions are: > > > 1. Why is the spanning tree re-learn if I just disconnect the > > blocking > > link > > > at SW2-gigastack (2)? > > > > CL: becasue you have still introduced a change. i.e. the link > > in question > > disappears > > > > > 2. Why is the spanning tree re-learn if I install a new > > switch? (I am sure > > > SW1 is still the root bridge) > > > > CL: becasue you are still introducing a change. STP runs > > because there > > exists the possibility that the new switch introduces a loop. > > it is also > > possible that the new switch has a better priority and is > > supposed to become > > the root bridge. > > > > > > > 3. I want to enable spanning portfast on all of the gigastack > > port. > > However, > > > I wonder will it cause network loop if I connect the SW2 and > > SW3 with > > > Gigastack? > > > > CL: portfast is not a real good idea for ports connected to > > other switches. > > the whole idea of STP is to ensure loop free topologies. you are > > deliberately bypassing the process that ensures loop free when > > you enable > > portfast. the whole idea of portfast is geared towards > > workstations that > > time out, thinking they are not connected to a network, during > > the time the > > STP is running. > > > > > > > 4. As the SW3 is on loan, I need to replace it after several > > months. Is > > that > > > means, the network connection between SW1 and SW2 will be > > interrupt again? > > > > CL: yes. so do the work after hours, if this is an issue. > > > > > > > > Please help! > > > > > > CL: given waht appears to be a small and more or less controlled > > environment, you can disable spanning tree, if you think you > > can assure loop > > free in general. STP is there to protect you, but in some > > environments it > > may not be necessary. > > > > > > > > > > > > Thanks, > > > Dovelet Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=51456&t=51454 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
