Nortel Networks WEB OS 212777 - Manual (Page 55)

Web OS 10.0 Application Guide
Chapter 2: VLANs n 55
212777-A, February 2002
VLAN Participation in Spanning Tree Groups
The VLAN participation for each Spanning Tree group in Figure 2-5 on page 53 is discussed in
the following sections:
n
VLAN 1 Participation
If Web switch A is the root bridge, then Web switch A will transmit the BPDU for VLAN
1 on ports 1 and 2. Web switch C receives the BPDU on its port 2 and Web switch D
receives the BPDU on its port 1. Web switch D will block port 8 or Web switch C will
block port 1 depending on the information provided in the BPDU.
n
VLAN 2 Participation
Web switch A, the root bridge generates another BPDU for Spanning Tree Group 2 and
forwards it out from port 8. Web switch B receives this BPDU on its port 1. Port 1 on Web
switch B is on VLAN 2, Spanning Tree group 1. Because Web switch B has no additional
ports participating in Spanning Tree group 1, this BPDU is not be forwarded to any addi-
tional ports and Web switch A remains the designated root.
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VLAN 3 Participation
For VLAN 3 you can have Web switch B or C to be the root bridge. If Web switch B is the
root bridge for VLAN 3, Spanning Tree group 2, then Web switch B transmits the BPDU
out from port 8. Web switch C receives this BPDU on port 8 and is identified as participat-
ing in VLAN 3, Spanning Tree group 2. Since Web switch C has no additional ports par-
ticipating in Spanning Tree group 2, this BPDU is not forwarded to any additional ports
and Web switch B remains the designated root.