How does iTest Lab optimizer performs reservation for topology with multiple switches (Z- links) ?

Environment/Versions

iTest Lab Optimizer (iLO)

Physical topology with Z-link

Answer

iLO builds a graph, which vertexes are physical topology ports, and edges are:

Physical links

Links between ports of the same parent resource, if this parent is a switch.

Then, it finds shortest paths between each pair of vertexes in this graph (using Floyd–Warshall algorithm). For each link from logical topology, we get the shortest path between its endpoints in physical topology. From this path, we determine, which ports on which switches need to be mapped/added to VLAN to activate this link.

Example: Consider the following physical topology:

and logical topology is A <-> B. Activation can be done in two ways: A – S1 – S2 – B and A – S1 – S3 – S2 – B. iLO deliberately chooses the first one, since it is shorter.

The same is true for L2 switches. If S1, S2 and S3 switches in the diagram above are L2 switches, iLO will create VLAN on S1 and S2 switches, leaving S3 switch intact.