Chapter 7 Spanning Tree
7.5 Application Example for STP Function
Network Requirements
Switch A, B, C, D and E all support MSTP function. A is the central switch.
B and C are switches in the convergence layer. D, E and F are switches in the access layer. There are 6 VLANs labeled as VLAN101-VLAN106 in the network.
All switches run MSTP and belong to the same MST region.
The data in VLAN101, 103 and 105 are transmitted in the STP with B as the root bridge. The data in VLAN102, 104 and 106 are transmitted in the STP with C as the root bridge.
Configuration Procedure Configure Switch A:
Step Operation Description
1 Configure ports On VLAN→802.1Q VLAN page, configure the link type of the related ports as Tagged, and add the ports to VLAN101-VLAN106. The detailed instructions can be found in the section 802.1Q VLAN.
2 Enable STP function On Spanning Tree→STP Config→STP Config page, enable STP function and select MSTP version.
On Spanning Tree→STP Config→Port Config page, enable MSTP function for the port.
3 Configure the region name and the revision of MST region
On Spanning Tree→MSTP Instance→Region Config page, configure the region as TP-LINK and keep the default revision setting.
4 Configure VLAN-to-Instance mapping table of the MST region
On Spanning Tree→MSTP Instance→Instance Config page, configure VLAN-to-Instance mapping table. Map VLAN 101, 103 and 105 to Instance 1; map VLAN 102, 104 and 106 to Instance 2.
Configure Switch B:
Step Operation Description
1 Configure ports On VLAN→802.1Q VLAN page, configure the link type of the related ports as Tagged, and add the ports to VLAN101-VLAN106. The detailed instructions can be found in the section 802.1Q VLAN.
2 Enable STP function On Spanning Tree→STP Config→STP Config page, enable STP function and select MSTP version.
On Spanning Tree→STP Config→Port Config page, enable MSTP function for the port.
3 Configure the region name and the revision of MST region
On Spanning Tree→MSTP Instance→Region Config page, configure the region as TP-LINK and keep the default revision setting.
4 Configure VLAN-to-Instance mapping table of the MST region
On Spanning Tree→MSTP Instance→Instance Config page, configure VLAN-to-Instance mapping table. Map VLAN 101, 103 and 105 to Instance 1; map VLAN 102, 104 and 106 to Instance 2.
5 Configure switch B as the root bridge of Instance 1
On Spanning Tree→MSTP Instance→Instance Config page, configure the priority of Instance 1 to be 0.
6 Configure switch B as the designated bridge of Instance 2
On Spanning Tree→MSTP Instance→Instance Config page, configure the priority of Instance 2 to be 4096.
Configure Switch C:
Step Operation Description
1 Configure ports On VLAN→802.1Q VLAN page, configure the link type of the related ports as Tagged, and add the ports to VLAN101-VLAN106. The detailed instructions can be found in the section 802.1Q VLAN.
2 Enable STP function On Spanning Tree→STP Config→STP Config
page, enable STP function and select MSTP version. On Spanning Tree→STP Config→Port Config
page, enable MSTP function for the port. 3 Configure the region name and
the revision of MST region
On Spanning Tree→MSTP Instance→Region Config page, configure the region as TP-LINK and keep the default revision setting.
4 Configure VLAN-to-Instance mapping table of the MST region
On Spanning Tree→MSTP Instance→Instance Config page, configure VLAN-to-Instance mapping table. Map VLAN101, 103 and 105 to Instance 1; map VLAN102, 104 and 106 to Instance 2.
5 Configure switch C as the root bridge of Instance 1
On Spanning Tree→MSTP Instance→Instance Config page, configure the priority of Instance 1 to be 4096.
6 Configure switch C as the root bridge of Instance 2
On Spanning Tree→MSTP Instance→Instance Config page, configure the priority of Instance 2 to be 0.
Configure Switch D:
Step Operation Description
1 Configure ports On VLAN→802.1Q VLAN page, configure the link type of the related ports as Tagged, and add the ports to VLAN101-VLAN106. The detailed instructions can be found in the section 802.1Q VLAN.
2 Enable STP function On Spanning Tree→STP Config→STP Config
page, enable STP function and select MSTP version. On Spanning Tree→STP Config→Port Config
page, enable MSTP function for the port. 3 Configure the region name and
the revision of MST region
On Spanning Tree→MSTP Instance→Region Config page, configure the region as TP-LINK and keep the default revision setting.
4 Configure VLAN-to-Instance mapping table of the MST region
On Spanning Tree→MSTP Instance→Instance Config page, configure VLAN-to-Instance mapping table. Map VLAN101, 103 and 105 to Instance 1; map VLAN102, 104 and 106 to Instance 2.
The topology diagram of the two instances after the topology is stable
For Instance 1 (VLAN101, 103 and 105), the red paths in the following figure are connected links; the gray paths are the blocked links.
For Instance 2 (VLAN102, 104 and 106), the blue paths in the following figure are connected links; the gray paths are the blocked links.
Suggestion for Configuration
Enable TC Protect function for all the ports of switches. Enable Root Protect function for all the ports of root bridges. Enable Loop Protect function for the non-edge ports.
Enable BPDU Protect function or BPDU Filter function for the edge ports which are connected to the PC and server.