HP ProCurve 9304M Installation And Configuration Manual page 274

Installation and Basic Configuration Guide
Figure 8.29 Customer using multiple spanning trees and SP using Single STP
tagged to multiple vlan
stp-boundary
untagged to vlan 100
Customer traffic from different VLANs is maintained by different spanning trees, while the SP network is
maintained by a single spanning tree. The SP can still use multiple VLANs at the core to separate traffic from
different customers. However, all VLANs will have the same network topology because they are all calculated by
the single spanning tree. The loop-free, non-blocking network acts like a hub for the customer network, with
boundary ports 2/1 on each device being untagged members of VLAN 100.
Traffic from all VLANs in the customer network will be aggregated through VLAN 100 at the SP. This setup leaves
the customer network's switching pattern virtually unchanged from the scenario in "Customer and SP Use Multiple
Spanning Trees" on page 8-67, since the SP network still is perceived as a virtual hub, and maintenance of the
hub's loop-free topology is transparent to the customer network.
Customer Uses Single STP But SP Uses Multiple Spanning Trees
Figure 8.30 shows an example of SuperSpan where the customer network uses Single STP while the SP uses
multiple spanning trees.
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R
10
1/1
Customer
Region
3/1
R
20
R
xx
Root bridge for VLAN xx
R
2/2
single
span
2/1
Provider
Region
2/1
2/2