Nortel business policy switch 2000, User Manual

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120 Chapter 2 Network configuration
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Figure 27 Possible problems with VLANs and Spanning Tree Protocol
As shown in Figure 27 , with STP enabled, only one connection between Switch
S1 and Switch S2 is forwarding at any time. Communications failure occurs
between VLAN 2 of S1 and VLAN 2 of S2, blocking communications between
Stations A and B.
The STP selects the link connecting VLAN 1 on Switches S1 and S2 as the
forwarding link based on port speed, duplex-mode, and port priority. Because the
other link connecting VLAN 2 is in Blocking mode, stations on VLAN 2 in
Switch S1 cannot communicate with stations in VLAN 2 on Switch S2. With
multiple links only one link will be forwarding.
Shared servers
Business Policy Switches allow ports to exist in multiple VLANs for shared
resources, such as servers, printers, and switch-to-switch connections. It is also
possible to have resources exist in multiple VLANs on one switch as shown in
Figure 28 .
In this example, clients on different broadcast domains share resources. The
broadcasts from ports configured in VLAN 3 can be seen by all VLAN port
members of VLAN 3.
S2
S1
VLAN 1
VLAN 2
VLAN 1 VLAN 2
Blocking
Station A
No
Communications
Station B
Forwarding
Business
Policy Switch 2000
Business
Policy Switch 2000
9801EA