Defining non-forwarding adjacencies in bipartite networks, such as clos newtorks, having a level 2 backbone and level 1 nodes

Abstract

Problems associated with providing a large Clos network having at least one top of fabric (ToF) node, a plurality of internal nodes, and a plurality of leaf nodes may be solved by: (a) providing L2 tunnels between each of the leaf nodes of the Clos and one or more of the at least one ToF node to ensure a non-partitioned IGP L2 backbone, and (b) identifying the L2 tunnels as non-forwarding adjacencies in link state topology information stored in ToF node(s) and leaf node(s) such that the L2 tunnels are not used for forwarding traffic. In some example implementations consistent with the present disclosure, the L2 tunnels are not used to compute routes from the link state topology information. Alternatively, in some other example implementations consistent with the present disclosure, the L2 tunnels are used to compute routes, but such routes are not used, or only used if no routes using only L1 (or L1-down adjacencies) are available. In some example implementations consistent with the present disclosure, L2 prefix information is leaked down to L1 of the IGP.