Nortel Networks WEB OS 212777 - Manual (Page 48)

Web OS 10.0 Application Guide
48 n Chapter 2: VLANs
212777-A, February 2002
Example 2: Parallel Links with VLANs
Figure 2-2 Example 2: Parallel Links with VLANs
The following items describe the features of this example:
n
Example 2 shows how it is possible, through the use of VLANs, to create configurations
where there are multiple links between two switches, without creating broadcast loops.
n
Two Alteon Web switches are connected with two different Gigabit Ethernet links. With-
out VLANs, this configuration would create a broadcast loop, but the STP topology reso-
lution process resolves parallel loop-creating links.
n
To prevent broadcast loops, port 7 is on VLAN 10 and VLAN 22, port 8 is on VLAN 32
and VLAN 109. Both switch-to-switch links are on different VLANs and, thus, are sepa-
rated into their own broadcast domains.
n
Ports 1 and 2 on both switches are on VLAN 10; ports 3 and 4 on both switches are on
VLAN 22; Ports 5 and 6 on both switches are on VLAN 32; port 9 on both switches are on
VLAN 109.
n
It is necessary to turn on Spanning Tree Protocol (STP) on at least one of the switch-to-
switch links or, alternately, turned on in both switches. STP Bridge Protocol Data Units
(BPDUs) will be transmitted out both Gigabit Ethernet ports and interpreted by the switch
that there is a loop to resolve.
n
Spanning Tree is VLAN-aware.
Link
Data
Active
Link
Data
Active
9 8
TX RX
TX RX
Power Console
5
TX RX
4
TX RX
3
TX RX
1
TX RX
2
TX RX
6
TX RX
Web Switch
10/100/10000 Mbps Ethernet Server Switch
7
TX RX
Link
Data
1000 Base-SX
Gigabit
Powered
Link
Data
Active
Link
Data
Active
9
8
TX RX
TX RX
Power Console
5
TX RX
4
TX RX
3
TX RX
1
TX RX
2
TX RX
6
TX RX
Web Switch
10/100/10000 Mbps Ethernet Server Switch
7
TX RX
Link
Data
1000 Base-SX
Gigabit
Powered
Gigabit Ethernet Port 8
VLAN #32, VLAN #109 Gigabit Ethernet Port 7
VLAN #10, VLAN #22
020