Basic Concepts In Pvst; How Pvst Works; Mstp; Mstp Features - HPE FlexFabric 5940 Series Configuration Manual

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The destination MAC address of a PVST BPDU is 01-00-0c-cc-cc-cd, which is a private MAC
address.
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Each PVST BPDU carries a VLAN tag. The VLAN tag identifies the VLAN to which the PVST
BPDU belongs.
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The organization code and PID fields are added to the LLC header of the PVST BPDU.
Figure 28 PVST BPDU format
A port's link type determines the type of BPDUs the port sends.
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An access port sends RSTP BPDUs.
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A trunk or hybrid port sends RSTP BPDUs in the default VLAN and sends PVST BPDUs in other
VLANs.

Basic concepts in PVST

PVST uses the same port roles and port states as RSTP for fast convergence. For more information,
see "Basic concepts in

How PVST works

In PVST, each VLAN runs RSTP independently to maintain its own spanning tree without affecting
the spanning trees of other VLANs. In this way, loops in each VLAN are eliminated and traffic of
different VLANs is load shared over links. PVST uses RSTP BPDUs in the default VLAN and PVST
BPDUs in other VLANs for spanning tree calculation. PVST of Hewlett Packard Enterprise
implements per-VLAN spanning tree calculation by mapping each VLAN to an MSTI.

MSTP

MSTP overcomes the following STP, RSTP, and PVST limitations:
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STP limitations—STP does not support rapid state transition of ports. A newly elected port
must wait twice the forward delay time before it transits to the forwarding state.
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RSTP limitations—Although RSTP enables faster network convergence than STP, RSTP fails
to provide load balancing among VLANs. As with STP, all RSTP bridges in a LAN share one
spanning tree and forward frames from all VLANs along this spanning tree.
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PVST limitations—Because each VLAN has its spanning tree, the amount of PVST BPDUs is
proportional to the number of VLANs on a trunk or hybrid port. When the trunk or hybrid port
permits too many VLANs, both resources and calculations for maintaining the VLAN spanning
trees increase dramatically. If a status change occurs on the trunk or hybrid port that permits
multiple VLANs, the device CPU will be overburdened with recalculating the affected spanning
trees. As a result, network performance is degraded.

MSTP features

Developed based on IEEE 802.1s, MSTP overcomes the limitations of STP, RSTP, and PVST. In
addition to supporting rapid network convergence, it allows data flows of different VLANs to be
forwarded along separate paths. This provides a better load sharing mechanism for redundant links.
RSTP."
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