NEC INTELLIGENT L2 SWITCH N8406-022A Application Manual

Also see for N8406-022A: Reference guide

Contents

NEC INTELLIGENT L2 SWITCH N8406-022A Application Manual Manual pdf 59 page image

RSTP and MSTP 59Multiple Spanning Tree ProtocolIEEE 802.1s Multiple Spanning Tree extends the IEEE 802.1w Rapid Spanning Tree Protocol through multipleSpanning Tree Groups. MSTP maintains up to 32 spanning-tree instances that correspond to STP Groups 1-32.In Multiple Spanning Tree Protocol (MSTP), several VLANs can be mapped to each Spanning-Tree instance. EachSpanning-Tree instance is independent of other instances. MSTP allows frames assigned to different VLANs tofollow separate paths, each path based on an independent Spanning-Tree instance. This approach providesmultiple forwarding paths for data traffic, enabling load balancing, and reducing the number of Spanning-Treeinstances required to support a large number of VLANs.MSTP regionA group of interconnected bridges that share the same attributes is called an MSTP region. Each bridge within theregion must share the following attributes:• Alphanumeric name• Revision level• VLAN-to-STG mapping schemeMSTP provides rapid reconfiguration, scalability, and control due to the support of regions, and multiple Spanning-Tree instances support within each region.Common Internal Spanning TreeThe Common Internal Spanning Tree (CIST) provides a common form of Spanning Tree Protocol, with oneSpanning Tree instance that can be used throughout the MSTP region. CIST allows the switch to interoperate withlegacy equipment, including devices that run IEEE 802.1D (STP).CIST allows the MSTP region to act as a virtual bridge to other bridges outside of the region, and provides a singleSpanning-Tree instance to interact with them.CIST is the default spanning tree group. When VLANs are removed from STG 1-32, the VLANs automaticallybecome members of the CIST.CIST port configuration includes Hello time, Edge port status (enable/disable), and Link Type. These parameters donot affect Spanning Tree Groups 1-32. They apply only when the CIST is used.MSTP configuration guidelinesThis section provides important information about configuring Multiple Spanning Tree Groups:• When you turn on MSTP, the switch automatically moves VLAN 1 to the Common Internal Spanning Tree(CIST).• Region Name and revision level must be configured. Each bridge in the region must have the same name andrevision level.• The VLAN and STP Group mapping must be the same across all bridges in the region.• You can move any VLAN to the CIST.• You can move VLAN 1 into any Spanning Tree Group.MSTP configuration exampleThis section provides steps to configure Multiple Spanning Tree Protocol on the switch, using the Command LineInterface (CLI) or the Browser-based Interface (BBI).Configuring Multiple Spanning Tree Protocol (CLI example)1. Configure port and VLAN membership on the switch, as described in the “Configuring ports and VLANs (CLIexample)” section in the “VLANs” chapter of this guide.2. Set the mode to Multiple Spanning Tree, and configure MSTP region parameters.>> /cfg/l2/ mrst (Select Multiple Spanning Tree menu)>> Multiple Spanning Tree# mode mstp (Set mode toMultiple Spanning Trees)>> Multiple Spanning Tree# on (Turn Multiple Spanning Trees on)>> Multiple Spanning Tree# name xxxxxx (Define the Region name)>> Multiple Spanning Tree: rev xx (Define the Region revision level)