1. A method of network planning for an Ethernet based network having a network topology and a plurality of VLANs to be associated therein wherein a number of routes is required through the network, the method comprising the steps of: determining a set of spanning trees within the network for providing one or more of the number of routes for consideration, wherein each spanning tree comprising a plurality of links; sorting the VLANs into an order based on one or more VLAN criteria for the network topology; mapping the sorted VLANs onto the set of spanning trees in an order to optimise one or more characteristics relating to the network or any associated feature thereof for the or each combination of spanning tree and VLAN to thereby determine an optimised VLAN tree mapping for each set of spanning trees for each route; selecting a best primary tree from the set of spanning trees for each route in the network topology according to the optimised VLAN tree mapping; analysing possible failures for each link in the best primary tree for each route to derive for each possible failure a backup tree which is optimised in terms of the characteristics and criteria to determine one or more best backup trees to replace the or each best primary tree in the event of a possible failure of the analysed possible failures; outputting information relating to the best primary tree and the determined one or more best backup trees for each best primary tree for each route in the network.