Figure 193: spanning regions - example 1 – Allied Telesis AT-S63 User Manual
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Chapter 24: Multiple Spanning Tree Protocol
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Section V: Spanning Tree Protocols
exists between the regions, and Switch B would block a port.
Figure 193. Spanning Regions - Example 1
There are several ways to address this issue. One is to have only one
MSTP region for each subnet in your network.
Another approach is to group those VLANs that need to span regions into
the same MSTI. Those VLANs that do not span regions can be assigned
to other MSTIs.
Here is an example. Assume that you have two regions that contain the
following VLANS:
Region 1 VLANs
Region 2 VLANs
Sales
Hardware Engineering
Presales
Software Engineering
Marketing
Technical Support
Advertising
Product Management
Technical Support
CAD Development
Product Management
Accounting
Project Management
Accounting
The two regions share three VLANs: Technical Support, Product
Management, and Accounting. You could group those VLANs into the
same MSTI in each region. For instance, for Region 1 you might group the
three VLANs in MSTI 11 and in Region 2 you could group them into MSTI
6. After they are grouped, you can connect the VLANs across the regions
using a link of tagged ports.
Region 1
Region 2
Switch A
Switch B
FAULT
RPS
MASTER
POWER
CLASS 1
LASER PRODUCT
STATUS
TERMINAL
PORT
1
3
5
7
9
11
2
4
6
8
10
12
13
15
17
19
21
23R
14
16
18
20
22
24R
AT-9424T/SP
Gigabit Ethernet Switch
1
3
5
7
9
11
13
15
17
19
21
23R
2
4
6
8
10
12
14
16
18
20
22
24R
23
24
L/A
D/C
D/C
L/A
D/C
L/A
1000 LINK / ACT
HDX / COL
FDX
10/100 LINK / ACT
PORT ACTIVITY
L/A
1000 LINK / ACT
SFP
SFP
24
SFP
23
FAULT
RPS
MASTER
POWER
GBIC
23
GBIC
24
CLASS 1
LASER PRODUCT
STATUS
TERMINAL
PORT
1
3
5
7
9
11
2
4
6
8
10
12
13
15
17
19
21
23R
14
16
18
20
22
24R
AT-9424T/GB
Gigabit Ethernet Switch
1
3
5
7
9
11
13
15
17
19
21
23R
2
4
6
8
10
12
14
16
18
20
22
24R
23
24
L/A
D/C
D/C
L/A
D/C
L/A
1000 LINK / ACT
HDX / COL
FDX
10/100 LINK / ACT
PORT ACTIVITY
L/A
1000 LINK / ACT
GBIC
Port 5
MSTI 4
VLAN (untagged) port: Accounting
Port 16
MSTI 12
VLAN (untagged port): Sales
VLAN (tagged port): Presales
VLAN (tagged port): Marketing