Chapter 11. Spanning Tree Protocols; Spanning Tree Protocol Modes - Lenovo Flex System Fabric CN4093 Application Manual

Chapter 11. Spanning Tree Protocols

Spanning Tree Protocol Modes

© Copyright Lenovo 2015
When multiple paths exist between two points on a network, Spanning Tree
Protocol (STP), or one of its enhanced variants, can prevent broadcast loops and
ensure that the CN4093 10Gb Converged Scalable Switch (CN4093) uses only the
most efficient network path.
This chapter covers the following topics:
 "Spanning Tree Protocol Modes" on page 145
 "Global STP Control" on page 146
 "PVSRT Mode" on page 146
 "Rapid Spanning Tree Protocol" on page 158
 "Multiple Spanning Tree Protocol" on page 160
"Port Type and Link Type" on page 164

Lenovo N/OS 8.2 supports the following STP modes:
 Rapid Spanning Tree Protocol (RSTP)
IEEE 802.1D (2004) RSTP allows devices to detect and eliminate logical loops in
a bridged or switched network. When multiple paths exist, STP configures the
network so that only the most efficient path is used. If that path fails, STP
automatically configures the best alternative active path on the network in order
to sustain network operations. RSTP is an enhanced version of IEEE 802.1D
(1998) STP, providing more rapid convergence of the Spanning Tree network
path states on STG 1.
See "Rapid Spanning Tree Protocol" on page
 Per‐VLAN Rapid Spanning Tree (PVRST+)
PVRST mode is based on RSTP to provide rapid Spanning Tree convergence, but
supports instances of Spanning Tree, allowing one STG per VLAN. PVRST
mode is compatible with Cisco R‐PVST/R‐PVST+ mode.
PVRST is the default Spanning Tree mode on the CN4093. See "PVSRT Mode"
on page 146 for details.
 Multiple Spanning Tree Protocol (MSTP)
IEEE 802.1Q (2003) MSTP provides both rapid convergence and load balancing
in a VLAN environment. MSTP allows multiple STGs, with multiple VLANs in
each.
See "Multiple Spanning Tree Protocol" on page
158 for details.
160 for details.
145