Turn spanning-tree portfast off or leave on

[Live2 Bicycle]

I just took over the net admin pos at this company. On 2924 swtches that are connected to other switches via a FE port spanning-tree portfast is turned on. On a bunch of others it is turned off. Which one is correct?

[Georg Pauwen]

Hello,

on ports connected to other switches, turn portfast off, on user ports, turn it on.

Here is the explanation:

A port configured with portfast skips the listening and learning phases of the spanning-tree protocol, and the port transitions directly to the forwarding state. Since the connected end stations are by definition stub connections, a spanning-tree loop cannot occur on these ports under normal circumstances. In addition to being unnecessary, running spanning-tree on ports that connect to end stations may result in undesirable effects. These effects may include hosts not being able to negotiate addresses through DHCP, or log on to a network domain.

HTH,

GP

[Live2 Bicycle]

Thank you for your responce. I found this article this evening that states what you wrote as well.

http://www.cisco.com/warp/public/473/12.html

[griffijo]

You definitely want it on, especially on switch-to-switch links. On other ports where you know you have devices such as workstations, servers, etc., you can use spanning-tree portfast; that will put the port into a forwarding state faster than if you were using spanning-tree in the default mode.

[sfrisby]

In some cases - turning on Spanning Tree Port-Fast on Layer 3 Links between switches can provide faster convergence. - where your absolutely sure there is no loop -

You can achieve faster network convergence when a switch comes back after a power down.

You have to be very careful - I have always turned on Port Fast on layer 3 point - point links to provide for faster recovery.