backbonefast, uplinkfast, and etherchannels

[wil_amaya]

Hi All. I'm preparing for my BSMSN exam and i'm a bit confused about something. Cisco book recommends the following:

Backbonefast - enabled on all swtiches in the network

UplinkFast - enabled on all wiring closet switches (access switches)

My question is this, if my trunks are made up of two or more ports in a bundle (etherchannel) and one fails, the network doesn't really notice it because there are other ports in the bundle that are already in forwarding mode. That said, when using an etherchannel for trunks, do you still need to have backbone fast and uplinkfast configured on your switches or is it no longer required? Any help is appreciated. thanks.

[ananddiwakar]

Uplinkfast etc are configured for a scenario where you will have multiple paths to reach the root switch.

In your case you are connecting access switch to (say) distribution switch with only one link (etherchannel). Here uplinkfast will not have any role to play.

In a typical scenario you will have two distribution switches and access switches will terminate on both these distribution switches with two separate links. Now if one of these links fail, STP will take its time to calculate the topology again and make the other path (through second Dx switch) active.

Uplinkfast and backbonefast will be used to avoid these time delays. Uplinkfast calculates backup paths and in case the active link fails, the backup link is immediately moved to forwarding state.