Fault tolerant LAN

[tw500]

I am looking to create a LAN using Cisco Catalyst 2950C switches (with the 2 fibre uplink ports) and I was thinking of connecting all the switches in a ring to create a fault tolerant topology. I am not too fussed about most of the client connections, and the server and critical client connections I can use dual attachment to a pair of switches. The distances between switches rules out the use of anything but fibre connections.

My question is will this work? Will the spanning tree create a logical "break" in the loop and will this re-arrange itself when a switch (or more likely a fibre) breaks?

Is there a better way to achieve this arrangement?

 

[hibit]

Hello tw500,

First off the answer to spanning tree is YES. Spanning tree will look for any and all loops in the network. However there are many more things to consider when setting up a fault tolerant layer 2. Some are:

1. Is a ring star or mesh the best layout?
Keep in mind that when a fault happens in the ring, data must hop all the way around the ring to get out. This might overrun the bandwith of a low power switch. Think of layer 2 HOPS in the same maner as ROUTER hops to the internet, more hops more latency. I normaly look for a mesh or partial mesh for the layer2. This gives me some flexability to provde redundant links where needed. Also you can do some load balancing if the client/server traffic patterns will allow. Under Cisco spanning tree you can also run multiple vlans and get multiple instances of Spantree.

2. Manufacture of switches.

You must make sure that all layer 2 devices run the same version of spantree. Some manufactures only support one version some all. Basically, if you have all Cisco then this issue is mute.


I would go to cisco web site to get some more data.

http://www.cisco.com.

There are lots of options that can help with failover (uplinkfast/backbonefast/portfast).

YOU MUST GET THE LAYER 2 RIGHT ELSE ALL WILL CRUMBLE fast!!!!!


good luck