3Com Switch 8800 Configuration Guide Chapter 38 MSTP Region-configuration38-36Operation CommandEnable STP global error or eventdebuggingdebugging stp { global-error |global-event }Disable STP global error or eventdebuggingundo debugging stp { global-error |global-event }38.4 Typical MSTP Configuration ExampleI. Network requirementsMSTP provides different forwarding paths for packets of different VLANs. Theconfigurations are as follows: all the switches in the network belong to the same MSTdomain, packets of VLAN 10 travels along instance 1, packets of VLAN 30 travels alonginstance 3, packets of VLAN 40 travels along instance 4, and that of VLAN 20 travelsalong 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 at theaccess layer only. So the root of instance 1 can be configured as Switch A, root ofinstance 3 can be Switch B, and root of instance 4 can be Switch C.II. Network diagramSwitch 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, 40Figure 38-9 Network diagram for MSTP configurationNote:The explanations on the above figure which goes like “permit: XXXX” means thatpackets of these VLANs are permitted to pass.
