1. A method for setting up and updating multiple trees in an Ethernet network having a plurality of bridges controlled in a link state manner wherein a topology database is available at each bridge and each bridge has a single forwarding tree, said method comprising: calculating the single forwarding tree at a root bridge of the tree or in a master bridge only; the root bridge advertising the calculated forwarding tree to other bridges participating in the forwarding tree; discarding the advertisement if it is determined by a particular bridge that information in the advertisement regarding neighboring bridges has already been learned by the particular bridge; configuring the forwarding tree according to the received advertisement by blocking ports not participating in the forwarding tree; further distributing the tree advertisement over non-blocked ports within the forwarding tree; analyzing potential failure events and assigning a probability of failure value to each event; and calculating one or more backup trees for events with a highest probability of failure.