User guide

8-4 E
XTREME
W
ARE
S
OFTWARE
U
SER
G
UIDE
S
PANNING
T
REE
P
ROTOCOL
(STP)
Figure 8-1: Multiple Spanning Tree Domains
When the switches in this configuration start up, STP configures each STPD such that
there are no active loops in the topology. STP could configure the topology in a number
of ways to make it loop-free.
In Figure 8-1, the connection between Switch A and Switch B is put into blocking state,
and the connection between Switch Y and Switch Z is put into blocking state. After STP
converges, all the VLANs can communicate, and all bridging loops are prevented.
The VLAN Marketing, which has not been assigned to either STPD1 or STPD2,
communicates using all five switches. The topology has no loops, because STP has
already blocked the port connection between Switch A and Switch B, and between
Switch Y and Switch Z.
Within a single STPD, you must be extra careful when configuring your VLANs.
Figure 8-2 illustrates a network that has been incorrectly set up using a single STPD so
that the STP configuration disables the ability of the switches to forward VLAN traffic.
Sales, Personnel, Marketing
STPD 1
STPD 2
Manufacturing, Engineering, Marketing
Sales, Personnel, Manufacturing, Engineering, Marketing
Switch A Switch Y
Switch Z
Switch M
Switch B
EW_011