How Many Hubs (Repeaters) Can be in a Single VG Network?
The answer is “it depends.” A VG network is like a 10Base-T Ethernet network. You can hook together lots of hubs. The 802.12 spec says “All topologies that are allowed (in terms of distances and numbers of repeaters) in clause 13 of ISO/IEC 8802-3 for collision domains of 10BASE-T and 10BASE-FL segments are allowed in demand priority access domains.” In English, you can plug together hubs much like 10Base-T hubs are connected. The only practical difference is that a VG network is built in a real tree where intermediate hubs and leaf hubs connect to their parent hubs via their uplink port. A hub’s uplink port can plug into any port of its parent hub, except the parent hubs uplink port (i.e., any regular port). The only real limiting factor in the number of hubs is the number of hub levels in a VG network. The specified limit is 5. In a VG network, there is always a root or level 1 hub. The root hub is either the only hub, or the hub that has one or more children hubs, and no parent hub
