EX2500 Ethernet Switch Configuration Guide
38 Per VLAN Rapid Spanning Tree
In Figure 8, VLAN 1 and VLAN 2 belong to different Spanning Tree Groups. The two
instances of Spanning Tree separate the topology without forming a loop. Both
VLANs can forward packets between the switches without losing connectivity.
Figure 8: Two VLANs, Each on a Different Spanning Tree Group
PVRST Configuration Guidelines
This section provides important information about configuring Per VLAN Rapid
Spanning Tree Groups:
By default, STGs 2 through 128 are empty, and STG 1 contains all configured
VLANs until individual VLANs are assigned to other STGs. The EX2500 switch
allows only one VLAN per STG, except for STG 1.
If the ports are tagged, each port sends out a special BPDU containing the
tagged information.
When a tagged port belongs to more than one STG, the egress BPDUs are
tagged to distinguish the BPDUs of one STG from those of another STG.
Configuring PVRST
This configuration shows how to configure PVRST+ on the switch.
1. Set the spanning-tree mode to PVRST+.
ex2500(config)# spanning-tree mode pvrst
2. Configure port membership for VLAN 1 and VLAN 2. Define the STGs for each
VLAN.
By default, port 1 is a member of VLAN 1, and VLAN 1 is assigned to STG 1.
Add port 2 to VLAN 2, and assign VLAN 2 to STG 2.
ex2500(config)# vlan 2
ex2500(config-vlan)# enable
ex2500(config-vlan)# member 2
ex2500(config-vlan)# stg 2
ex2500(config-vlan)# exit
Switch 1
VLAN 1, STG 1
Switch 2
VLAN 2, STG 2
VLAN 1 passes traffic on STG 1
VLAN 2 passes traffic on STG 2
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