Medium-Sized Switched Network Construction

PVST+ (Per-VLAN Spanning Tree Protocol)

On this topology Two VLANs, one equal 10 and second equal 20, are being

trunked across these links.

objectif is to configure S3 as the root bridge forVLAN 20 and S1 as the root

bridge for VLAN 10.

Port F0/3 on S2 is the forwarding port for VLAN 20 and the blocking port for

VLAN 10. Port F0/2 on S2 is

the forwarding port for VLAN 10 and the blocking port for VLAN 20.

Activate pvst

Verify pvst ieee

Primary and Secondary Root Bridges for Each VLAN on S3

S3(config)#  spanning-tree vlan 20 root primary
S3(config)# spanning-tree vlan 10 root secondary

Primary and Secondary Root Bridges for Each VLAN on S1

S1(config)# spanning-tree vlan 10 root primary
S1(config)# spanning-tree vlan 20 root secondary

Configuring the Lowest Possible Priority to Ensure That a Switch Is Root

S3(config)#  spanning-tree vlan 20 priority 4096

S1(config)# spanning-tree vlan 10 priority 409

Guide to Multiple Spanning Tree Protocol

Introduction

MSTP or Multiple spanning tree protocol is based on IEEE 802.1s standard. MSTP is a protocol which maps multiple VLANs to a single instance.
Before MSTP, normal STP 802.1d or Rapid STP 802.1 which maps single vlan to a single STP instance. MSTP uses the rapid spanning tree protocol features
such as fast convergence, port states, port roles, edge ports and link types. However, with these functionalities, MSTP has also added some new features like regions, instances and mapping.

Configure the hostname of each switch as SW1, SW2, and SW3
Set the domain vtp mode as server and domain name as “marwat”
Establish a trunk link among all three switches.

Cérate 15 vlans from vlan 6 to vlan 20 at switch 1.

MSTP Configuration

We will define each MST command in the screenshots below. Go to global configuration mode and configure spanning-tree mode as most.

Enter into mst configuration through the following command

Set the revision number from 0 to 4094;

Map the VLANs from 6 to 12 with MST instance. There were 16 multiple spanning tree instances in the old IOS, but now it supports 4095 instances. It is the first mst instance on the switch.