Patent ID: 8787154

Claim:
A method comprising: receiving, with a multi-topology path computation element, topology information for a base network layer of a multi-topology network that comprises the base network layer having a plurality of network switches interconnected by base network layer three (L3) links in a base network topology and also comprises an overlay network layer having a plurality of overlay switches interconnected by overlay network links in an overlay network topology, wherein each of the overlay network links represents a path through the base network connecting two of the overlay switches; receiving, with the multi-topology path computation element, topology information for the overlay network layer, receiving, with the multi-topology path computation element, a path request that specifies two endpoints and a start time for path activation; determining, by the multi-topology path computation element, respective layers of the multi-topology network in which each of the two endpoints is logically located; computing, by the multi-topology path computation element, a path to carry traffic between the two endpoints through one or more layers of the multi-topology network using the topology information for the base network layer and the topology information for the overlay network layer, wherein computing the path comprises responsive to determining that a first one of the two endpoints is logically located in the overlay network layer and a second one of the two endpoints is logically located in the base network layer, computing a first sub-path of the path between one of the overlay switches having an interface to the first one of the two endpoints and a gateway connecting the overlay network layer and the base network layer and computing a second sub-path of the path between one of the network switches having an interface to the second one of the two endpoints and the gateway; scheduling, by the multi-topology path computation element, the computed path as a scheduled path for the start time; and installing, at the start time and by the multi-topology path computation element, forwarding information for the path to one or more of the network switches and overlay switches and also installing forwarding information for the path to the gateway to connect the first sub-path and the second sub-path in the gateway.