Shulou(Shulou.com)06/01 Report--

Spanning tree species

Stp rstp pvst mstp

Stp introduction

STP (Spanning Tree Protocol) is an acronym for spanning Tree Protocol. The protocol can be used to establish a tree topology in the network, eliminate the two-layer loop in the network, and achieve path redundancy through certain methods, but not necessarily. Spanning Tree Protocol is suitable for all manufacturers' network devices, and it is different in configuration and functional strength, but it is consistent in principle and application effect.

Function introduction

The main application of spanning Tree Protocol is to avoid single point of failure and network loopback in LAN, and to solve the problem of "broadcast storm" in ring Ethernet networks. in a sense, it is a kind of network protection technology. circular connections caused by errors or accidents can be eliminated. STP also provides the possibility of backup connection for the network, which can be combined with SDH protection to form the dual protection of the Ethernet ring network. The new Ethernet veneer supports spanning tree protocol STP which conforms to IEEE 802.1d standard and rapid spanning tree protocol RSTP specified by IEEE 802.1w, and the convergence speed can reach 1s.

Running process

Spanning Tree Protocol runs the spanning Tree algorithm (STA). The spanning tree algorithm is very complex, but its process can be summarized into the following three parts.

(1) Select the root bridge

(2) Select the root port

(3) Select the designated port (also known as forwarding port in some books)

Pvst introduction

PVST is a CISCO-specific solution for processing spanning trees in virtual intranets. PVST runs a separate spanning tree instance for each virtual local area network. in general, PVST requires CISCO's ISL to run on the trunk link between switches.

Use

Each VLAN spanning tree (PVST) maintains one spanning tree instance for each VLAN configured in the network. It uses ISL relays and allows a VLAN relay to forward some VLANs when blocked by other VLANs. Although PVST treats each VLAN as a separate network, it has the ability (at layer 2) to load balance communication through some VLANs in the backbone and other Vlans that does not cause spanning tree loops in another trunk.

Shortcoming

Since each VLAN needs to generate a tree, the traffic of the PVST BPDU will be proportional to the number of VLAN of the Trunk.

When the number of VLAN is relatively large, the amount of computation and resource consumption of maintaining multiple spanning trees will increase rapidly. Especially when Trunk changes the interface state of a lot of VLAN, all spanning tree states have to be recalculated, and the CPU will be overwhelmed. Therefore, the Cisco switch limits the number of VLAN used, and it is not recommended to Trunk many VLAN on one port.

Because of the private nature of the protocol, PVST/PVST+ can not be supported as widely as STP/RSTP. Devices from different manufacturers can not directly communicate with each other in this mode, but can only be implemented through some flexible ways, such as Foundry's IronSpan. IronSpan runs the STP protocol by default, and when a port receives PVST BPDU, the spanning tree mode of that port is automatically switched to PVST/PVST+ compatibility mode.

Basic principles of MSTP

Associate (map) multiple vlan to one instance (instance). Instance 0 (including all vlan) already exists by default. Usually, custom instances 1 and 2 have different roots, can be load balanced, and have the fast convergence of RSTP.

A switching network is divided into multiple domains through MSTP, and multiple spanning trees are formed in each domain, and the spanning trees are independent of each other. Each spanning tree is called a multiple spanning tree instance MSTI (Multiple Spanning Tree Instance), and each domain is called an MST MST Region:Multiple Spanning Tree Region.

Mstp advantage

By deploying MSTP multiple processes, you can do the following:

It greatly improves the deployability of spanning tree protocol under different networking conditions.

In order to ensure the reliable operation of networks running different types of spanning tree protocols, different types of spanning tree protocols can be divided into different processes, and the networks corresponding to different processes carry out independent spanning tree protocol calculation.

Enhance the reliability of the network, for a large number of layer 2 access equipment, can reduce the impact of a single equipment failure on the whole network.

Through the process isolation of different topology calculations, that is, the failure of a device only affects the corresponding topology of the process in which it is located, and will not affect the topology calculation of other processes.

When the network capacity is expanded, the maintenance amount of network managers can be reduced, thus improving the convenience of user operation and maintenance management.

When the network capacity is expanded, it is only necessary to divide the new process to connect with the original network, and there is no need to adjust the MSTP process configuration of the original network. If the device capacity is expanded in a process, you only need to modify it for the expanded process, and you do not need to adjust the configuration in other processes.

Realize layer 2 Port Segmentation Management

Each MSTP process can manage part of the ports on the device, that is, the layer 2 port resources of the device are divided and managed by multiple MSTP processes, and each MSTP process can run standard MSTP.

Rstp introduction

RSTP: rapid spanning Tree Protocol (rapid spanning Tree Protocol): 802.1w is developed from 802.1d, which can converge the network faster when the network structure changes. It has one more port type than 802.1d: the backup port (backup port) type, which is used for backup of designated ports. STP (Spanning Tree Protocol) is an acronym for spanning Tree Protocol. The protocol can be applied to the loop network to achieve path redundancy through certain algorithms, and at the same time, the loop network is trimmed into a tree network without loop, so as to avoid the proliferation and infinite circulation of packets in the loop network.

Function introduction

The main application of spanning Tree Protocol is to avoid the network loopback in the local area network and to solve the "broadcast storm" problem of the looped Ethernet network. in a sense, it is a kind of network protection technology. circular connections caused by errors or accidents can be eliminated. STP also provides the possibility of backup connection for the network, which can be combined with SDH protection to form the dual protection of the Ethernet ring network. The new Ethernet veneer supports spanning tree protocol STP in accordance with ITU-T 802.1d standard and rapid spanning tree protocol RSTP specified in 802.1w, and the convergence speed can reach 1s.

Mstp configuration

Topological graph

Stp rstp pvst mstp

Configuration mode

Configure Device A

Configure the domain name of the MST domain as example, and set the VLAN 10, 30, 40

Map to MSTI 1, 3, 4, respectively, and configure MSTP with a revision level of 0.

System-view

[DeviceA] stp region-configuration

[DeviceA-mst-region] region-name example

[DeviceA-mst-region] instance 1 vlan 10

[DeviceA-mst-region] instance 3 vlan 30

[DeviceA-mst-region] instance 4 vlan 40

[DeviceA-mst-region] revision-level 0

Activate the configuration of the MST domain.

[DeviceA-mst-region] active region-configuration

[DeviceA-mst-region] quit

Configure the root bridge where this device is MSTI 1.

[DeviceA] stp instance 1 root primary

Global enable spanning Tree Protocol.

[DeviceA] stp global enable

Configure Device B

Configure the domain name of the MST domain as example, and set the VLAN 10, 30, 40

Map to MSTI 1, 3, 4, respectively, and configure MSTP with a revision level of 0.

System-view

[DeviceB] stp region-configuration

[DeviceB-mst-region] region-name example

[DeviceB-mst-region] instance 1 vlan 10

[DeviceB-mst-region] instance 3 vlan 30

[DeviceB-mst-region] instance 4 vlan 40

[DeviceB-mst-region] revision-level 0

Activate the configuration of the MST domain.

[DeviceB-mst-region] active region-configuration

[DeviceB-mst-region] quit

Configure the root bridge where this device is MSTI 3.

[DeviceB] stp instance 3 root primary

Global enable spanning Tree Protocol.

[DeviceB] stp global enable

Configure Device C

Configure the domain name of the MST domain as example, and set the VLAN 10, 30, 40

Map to MSTI 1, 3, 4, respectively, and configure MSTP with a revision level of 0.

System-view

[DeviceC] stp region-configuration

[DeviceC-mst-region] region-name example

[DeviceC-mst-region] instance 1 vlan 10

[DeviceC-mst-region] instance 3 vlan 30

[DeviceC-mst-region] instance 4 vlan 40

[DeviceC-mst-region] revision-level 0

Activate the configuration of the MST domain.

[DeviceC-mst-region] active region-configuration

[DeviceC-mst-region] quit

Configure the root bridge where this device is MSTI 4.

[DeviceC] stp instance 4 root primary

Global enable spanning Tree Protocol.

[DeviceC] stp global enable

Configure Device D

Configure the domain name of the MST domain as example, and set the VLAN 10, 30, 40

Map to MSTI 1, 3, 4, and configure

The revision level for MSTP is 0.

System-view

[DeviceD] stp region-configuration

[DeviceD-mst-region] region-name example

[DeviceD-mst-region] instance 1 vlan 10

[DeviceD-mst-region] instance 3 vlan 30

[DeviceD-mst-region] instance 4 vlan 40

[DeviceD-mst-region] revision-level 0

Activate the configuration of the MST domain.

[DeviceD-mst-region] active region-configuration

[DeviceD-mst-region] quit

Global enable spanning Tree Protocol.

[DeviceD] stp global enable

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