Dell Networking N4000 Series Configuration Manual page 731

Figure 22-7. RSTP-PV and RSTP Interoperability
Root for VLAN2 and 3
SW1
1/0/2
SW3 sends IEEE STP BPDUs to the IEEE multicast MAC address as
untagged frames. These BPDUs are processed by the VLAN 1 STP instance
on the RSTP-PV switch as part of the VLAN 1 STP instance.
The RSTP-PV side sends IEEE STP BPDUs corresponding to the VLAN 1
STP to the IEEE MAC address as untagged frames across the link. At the
same time, SSTP BPDUs are sent as untagged frames. IEEE switches simply
flood the SSTP BPDUs throughout VLAN 1. This facilitates RSTP-PV
connectivity in case there are other RSTP-PV switches connected to the IEEE
STP domain.
For non-native VLANs (VLANs 2–4093), the RSTP-PV switch sends SSTP
BPDUs, tagged with their VLAN number. The VLAN STP instances are
multicast across the RSTP region, as if it were a hub switch.
1/0/1
1/0/3
VLAN1
VLAN2
VLAN3
Configuring the Spanning Tree Protocol
1/0/4
Root for VLAN1
SW3
1/0/1
SW2
1/0/1
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