HP NonStop G-Series - Manual (Page 269)

Migrating to the Layered Topology
The layered topology requires HP NonStop ServerNet Switches (model 6780).
To migrate a ServerNet cluster from one of the star topologies to the layered topology, you must have on hand enough
6780 switches and ServerNet cables to support your cluster. You need at least two switches (one for each external
fabric) for every eight nodes.
For details on planning a migration to the layered topology, including hardware, software, and cabling requirements,
see the ServerNet Cluster 6780 Planning and Installation Guide.
For a quick reference on cable connections, see Cable Connections in a Layered Topology .
Migrating to the Layered Topology 269