Information About Rapid Pvst; Stp; Overview Of Stp - Cisco Nexus 7000 Series Configuration Manual

Information About Rapid PVST+

Information About Rapid PVST+

The Spanning Tree Protocol (STP) was implemented to provide a loop-free network at Layer 2 of the network.
Rapid PVST+ is an updated implementation of STP that allows you to create one spanning tree topology for
each VLAN. Rapid PVST+ is the default STP mode on the device.
Note Spanning tree is used to refer to IEEE 802.1w and IEEE 802.1s. If the IEEE 802.1D Spanning Tree Protocol
is discussed in this publication, then 802.1D is stated specifically.
The Rapid PVST+ protocol is the IEEE 802.1w standard, Rapid Spanning Tree Protocol (RSTP), implemented
on a per VLAN basis. Rapid PVST+ interoperates with the IEEE 802.1Q VLAN standard, which mandates
a single STP instance for all VLANs, rather than per VLAN.
Rapid PVST+ is enabled by default on the default VLAN (VLAN1) and on all newly created VLANs on the
device. Rapid PVST+ interoperates with devices that run legacy IEEE 802.1D STP.
RSTP is an improvement on the original STP standard, 802.1D, which allows faster convergence.
The device supports full nondisruptive upgrades for Rapid PVST+. See the Cisco Nexus 7000 Series
Note
NX-OS High Availability and Redundancy Guide for complete information on nondisruptive upgrades.

STP

STP is a Layer 2 link-management protocol that provides path redundancy while preventing loops in the
network.

Overview of STP

In order for a Layer 2 Ethernet network to function properly, only one active path can exist between any two
stations. STP operation is transparent to end stations, which cannot detect whether they are connected to a
single LAN segment or a switched LAN of multiple segments.
When you create fault-tolerant internetworks, you must have a loop-free path between all nodes in a network.
The STP algorithm calculates the best loop-free path throughout a switched Layer 2 network. Layer 2 LAN
ports send and receive STP frames, which are called Bridge Protocol Data Units (BPDUs), at regular intervals.
Network devices do not forward these frames but use the frames to construct a loop-free path.
Multiple active paths between end stations cause loops in the network. If a loop exists in the network, end
stations might receive duplicate messages and network devices might learn end station MAC addresses on
multiple Layer 2 LAN ports.
STP defines a tree with a root bridge and a loop-free path from the root to all network devices in the Layer 2
network. STP forces redundant data paths into a blocked state. If a network segment in the spanning tree fails
and a redundant path exists, the STP algorithm recalculates the spanning tree topology and activates the
blocked path.
When two Layer 2 LAN ports on a network device are part of a loop, the STP port priority and port path-cost
setting determine which port on the device is put in the forwarding state and which port is put in the blocking
Cisco Nexus 7000 Series NX-OS Layer 2 Switching Configuration Guide, Release 5.x
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Configuring Rapid PVST+ Using Cisco NX-OS