152 CHAPTER 17: MSTP REGION- CONFIGURATIONTypical MSTPConfigurationExampleNetwork requirementsMSTP provides different forwarding paths for packets of different VLANs. Theconfigurations are as follows: all the switches in the network belong to the sameMST region, packets of VLAN 10 travels along instance 1, packets of VLAN 30travels along instance 3, packets of VLAN 40 travels along instance 4, and that ofVLAN 20 travels along instance 0.In the following network diagram, Switch A and Switch B are devices of theconvergence layer, Switch C and Switch D are devices of the access layer. VLAN 10and 30 function at the distribution and access layers, and VLAN 40 functions atthe access layer only. So the root of instance 1 can be configured as Switch A, rootof instance 3 can be Switch B, and root of instance 4 can be Switch C.Network diagramFigure 31 Network diagram for MSTP configurationn The explanations on the above figure which goes like "permit: XXXX" means thatpackets of these VLANs are permitted to pass.Enable debugging of the state machinefor port state transition undo debugging stp state-machine pstEnable debugging of the topologychange state machine debugging stp state-machine tcmDisable debugging of the topologychange state machine undo debugging stp state-machine tcmEnable debugging of the state machinefor port protocol transition debugging stp state-machine ppmDisable debugging of the state machinefor port protocol transition undo debugging stp state-machine ppmEnable debugging of the port transportstate machine debugging stp state-machine ptxDisable debugging of the port transportstate machine undo debugging stp state-machine ptxEnable debugging of the state machinefor topology change protection debugging stp state-machine tcpmDisable debugging of the state machinefor topology change protection undo debugging stp state-machine tcpmTable 136 Display and debug MSTPOperation CommandSwitch ASwitch CSwitch BSwitch DPermit :VLAN 10, 20Permit :VLAN 10, 20 Permit :VLAN 20, 30Permit :VLAN 20, 30Permit :all VLANPermit :VLAN 20, 40Switch ASwitch CSwitch BSwitch DPermit :VLAN 10, 20Permit :VLAN 10, 20 Permit :VLAN 20, 30Permit :VLAN 20, 30Permit :all VLANPermit :VLAN 20, 40
