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 topology database is available at each network node and each bridge has a single forwarding tree, said method comprising: calculating the single forwarding tree at a root bridge; the root bridge advertising the forwarding tree to other bridges participating in the forwarding tree; configuring the forwarding tree according to the received advertisement; distributing the tree advertisement only within the forwarding tree.