HP 445946-001 - Manual (Page 72)

Spanning Tree Protocol
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Figure 9 Two VLANs on one instance of Spanning Tree Protocol
In the following figure, VLAN 1 and VLAN 2 belong to different Spanning Tree Groups. The two instances
of spanning tree separate the topology without forming a loop, so that both VLANs can forward packets
between the switches without losing connectivity.
Figure 10 Two VLANs on separate instances of Spanning Tree Protocol
VLAN participation in Spanning Tree Groups
The following table shows which switch ports participate in each Spanning Tree Group. By default, server
ports (ports 1-16) do not participate in Spanning Tree, even though they are members of their respective
VLANs.
Table 12 VLAN participation in Spanning Tree Groups
VLAN 1 VLAN 2
Switch 1 Spanning Tree Group 1
Port 20 Spanning Tree Group 2
Port 21
Switch 2 Spanning Tree Group 1
Port 20 Spanning Tree Group 2
Port 21