Rapid Pvst+ Interoperation With 802.1S Mst - Cisco Nexus 9000 Series Configuration Manual

Rapid PVST+ Interoperation with 802.1s MST

Rapid PVST+ are version 2. If the BPDU received is an 802.1w BPDU version 2 with the proposal flag set,
the device sends an agreement message after all of the other ports are synchronized. If the BPDU is an 802.1D
BPDU version 0, the device does not set the proposal flag and starts the forward-delay timer for the port. The
new root port requires twice the forward-delay time to transition to the forwarding state.
The device interoperates with legacy 802.1D devices as follows:
• Notification—Unlike 802.1D BPDUs, 802.1w does not use TCN BPDUs. However, for interoperability
• Acknowledgment—When an 802.1w device receives a TCN message on a designated port from an
• Protocol migration—For backward compatibility with 802.1D devices, 802.1w selectively sends 802.1D
Note If you want all devices on the same LAN segment to reinitialize the protocol on each interface, you must
reinitialize Rapid PVST+.
Rapid PVST+ Interoperation with 802.1s MST
Rapid PVST+ interoperates seamlessly with the IEEE 802.1s Multiple Spanning Tree (MST) standard. No
user configuration is needed. To disable this seamless interoperation, you can use PVST Simulation.
High Availability for Rapid PVST+
The software supports high availability for Rapid PVST+. However, the statistics and timers are not restored
when Rapid PVST+ restarts. The timers start again and the statistics begin from 0.
See the Cisco Nexus 9000 Series NX-OS High Availability and Redundancy Guide, for complete information
Note
on high-availability features.
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with 802.1D devices, the device processes and generates TCN BPDUs.
802.1D device, it replies with an 802.1D configuration BPDU with the TCA bit set. However, if the
TC-while timer (the same as the TC timer in 802.1D) is active on a root port connected to an 802.1D
device and a configuration BPDU with the TCA set is received, the TC-while timer is reset.
This method of operation is required only for 802.1D devices. The 802.1w BPDUs do not have the TCA
bit set.
configuration BPDUs and TCN BPDUs on a per-port basis.
When a port is initialized, the migrate-delay timer is started (specifies the minimum time during which
802.1w BPDUs are sent), and 802.1w BPDUs are sent. While this timer is active, the device processes
all BPDUs received on that port and ignores the protocol type.
If the device receives an 802.1D BPDU after the port migration-delay timer has expired, it assumes that
it is connected to an 802.1D device and starts using only 802.1D BPDUs. However, if the 802.1w device
is using 802.1D BPDUs on a port and receives an 802.1w BPDU after the timer has expired, it restarts
the timer and starts using 802.1w BPDUs on that port.
Configuring Rapid PVST+ Using Cisco NX-OS