Im about to configure two Catalyst4506 with Sup4 as core switches that should replace the old Catalyst4003. Catalyst3500XL and Catalyst2950G are uses as access-layer switches, they are all running the last IOS release.
I want to minimize the convergence time if one of the switches fails. I have configured Spanning-tree uplinkfast on the access-layer switches. I have read about Backbone fast but this feature are not supported on Catalyst3500XL. Should I use the Backbone fast feature on the c4506 and c2950G? Will Backbone fast be useful since not all access-layer switches support this feature?
Do you have other useful tips that can reduce convergence time on my network?
You can tweak the Spanning Tree timers from their defaults, to shorten normal STP convergence time of 30 to 50 seconds to something quicker. But don't do this unless you completely understand your network's topology and what you're doing.
Here's a couple of helpful links:
Understanding and Tuning Spanning Tree Protocol Timers
(Sorry for the long URLs. If you can't click it directly, highlight the whole link and copy/paste it to your browser; or just go to the http://www.ciscopress.com web site and look for the "Cisco LAN Switching" book, you can find the sample chapters there.)
Also, depending on your network design (that is, how your VLANs and Layer3 switching are set up, protocols in use, etc.) maybe tuning STP convergence is not the answer; maybe looking at leveraging HSRP is. But it seems like you're interested in STP.
Also, not sure if all your switches can do Rapid STP (802.1w) or Multiple STP (802.1s). Check into links off the first link I gave you to learn about these; maybe someone else can chime in with exact switch models and software revisions that support these variants of STP.
I have tweaked one customer's STP timers to get convergence time down to about half of what's normal, after reading all of the above; works OK. But almost all the others' networks were better served by the STP defaults, or by taking advantage of HSRP and multigroup HSRP.
My opinion (confirmed by the expert) is that it should be possible to use it if all non-backboneFast switches are access ones. (See "Ask the expert - Spanning Tree Protocol" discussion, there are also some other usefull tips.
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