About Stacking Technology

Stacking technology

Stacking (Stack) and cascading (uplink) are two ways that multiple switches or hubs are connected together. Their primary purpose is to increase the port density. But the way they're implemented is different. Simply put, cascading can be done between switches in any network device manufacturer, between hubs, or between switches and hubs, via a twisted pair. Stacking is only possible between the devices of your own manufacturer, and this device must have a stacking capability. Cascading requires only a single twisted pair ( or other medium ), and stacksrequire dedicated stacking modules and stacking cables, which may need to be purchased separately. The cascade of switches is theoretically not limited by the number of cascading limits ( Note: The number of hubs cascade is limited, and The requirements of 10M and 100M are different), and the devices stacked by each manufacturer will indicate the maximum number of stacks.

It can be seen from the above that cascading is relatively easy, but stacking this technology has the advantage of cascading not achievable. First, multiple switches are stacked together, logically, they belong to the same device. This way, if you want to set up these switches, you can see other switches in the stack as long as you are connected to any one device. cascaded devices are logically independent, and if you want to network these devices, you must connect to each device in turn.

second, multiple device-level associations create cascading bottlenecks. For example, two gigabit switches cascade through a twisted pair, and their cascade bandwidth is hundred megabytes. So the computer between the different switches to communicate, all can only pass through this hundred megabytes bandwidth. While two switches are stacked together, stacking cables will provide over 1G of backplane bandwidth, greatly reducing bottlenecks. Now the switch has a

The new technology --port trunking, through which multiple twisted-pair wires can be cascaded between two switches, which multiplies the cascade bandwidth exponentially.

cascading also has a stack that does not reach the purpose of increasing the connection distance. For example, if a computer is farther away from the switch than the maximum distance of a single twisted pair , a switch can be placed in the middle to connect the computer to the switch. The stacking cable is only a few meters long, so it should be considered when stacking.

stacking and cascading each have advantages, in the actual design of the project often at the same time, can be flexibly applied.

Cascading is connected to other hubs through a hub port, and the stack is connected through the hub's backplane. Although cascading and stacking can enable the expansion of the number of ports, each hub or switch after cascading is logically still a plurality of managed devices, and the stack of several hubs or switches is logically a managed device.

Super Stacking: Extend the stacking distance with gigabit twisted pair or fiber optic cables!

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3750 Stacking

Unlike 3550,3750 is a real stack,and the Catalyst 3750 series uses stackwise Technology, an innovative stacking architecture that provides a the 32Gbps stack interconnect connects up to 9 switches and integrates them into a unified, logical, converged, optimized device that allows customers to deploy voice, video, and data applications with greater confidence. 3750 do stacking requires a dedicated stacking cable, the product comes with 0.5 meter stacking cable.

1. Basic requirements: iOS version to be consistent, stacking modules and stacking cables, the maximum number of stacks 9.

2.3750 uses the way the backplane is stacked, the machine itself has a stacking port to be dedicated stacking line to achieve 32G bandwidth

3. After the switch is stacked, logically, they belong to the same device. This way, if you want to set up these switches, you can see other switches in the stack as long as you are connected to any one device.

4. Stacking Advantages: High-density ports, easy to manage

5. There are two types of stacking:

① hard stacking, that is, with dedicated stacking hardware to achieve high-speed transmission, up to 4G transmission speed, hard-stacked representative of the star stack

② Soft Stacking, he uses the general gigabit port to connect, also can be seen as a gigabit port cascade, through the switch software to implement some stacking functions, such as master switch management from the switch, soft stack represents the daisy chain stack

6. Example:

3750 Stacking technology, using dedicated stacking cables, stacking the back panel to multiply the configuration shows a switch with different slot numbers such as SW1 and sw2 stacking The port information displayed

Interface GIGABITETHERNET0/8 (SW1)

Interface GIGABITETHERNET1/8 (SW2)

How do I differentiate between master and slave?

Line Plug Good , automatic stack election on boot , The Lord is the one who lights Master.

SH switch will be able to see

more intuitive is to see the lights

Mode hits stack, which led is the stack number of this switch

The master light is lit.

The machines are stacked with the PNs and can be seen on the command line as a single machine .

7. Stacking Steps :

1: Physical connection Good stacking cable , connection method for master Stack1 connected to slave stack2 above.

2: open master, do not make any configuration. And so on after the full boot.

3: open the slave machine.

4: Do not make any configuration.

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3750 Stacking Technology:

Basic requirement: Same system version

Up to 9 stacks with up to 32G bandwidth via one address management stack

Note: Stacking to ring

#showplatform Stack-manager All

#showswitch

#showswitch 1

#showswitch Detail

#showswitch Neighbors

#show Switch Stack-ports

Example :

Configure as the main switch as follows:

Switch 1 provision ws-c3750g-12s

Switch 1 PRIORITY15

Switch 2 provisionws-c3750g-24s

Switch 2 PRIORITY14

Switch 3 provisionws-c3750g-48s

Switch 3 PRIORITY13

SDM prefer desktop

Copy Running-config Startup-config

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Deep Stacking

Stacking lines into loops to achieve the effect of redundancy. When you unplug one of the stacked lines, the stacking group automatically restarts. After a reboot, the stacking group rebuilds the stack, providing redundancy.

the superimposed switches are connected by two loops. The hardware of the switch is responsible for load balancing the packets on a dual loop. The loop here acts as the backplane of this large logical switch, with the transfer rate of 32Gbps on the logical switch when both loops are working properly .

when a data frame needs to be transferred, the switch's software calculates which loop is more usable, and then the data frame is sent to the loop. If a stacked cable fails, the switch on both sides of the fault detects the failure and disconnects the affected loop, while the logical switch can still operate in a single-loop state, at which time the packet pass rate is 16Gbps.

reference:http://wenku.baidu.com/view/e30e240702020740be1e9b36.html(DCN)

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all single devices in the IRF stack are called member devices. Member devices are divided into two roles, depending on their functionality:

Master: One of the member devices that is elected by the role, which manages the entire stack . Only one member device can be a Master device at the same time in a stack .

Slave: A member device that is elected by a role, which is subordinate to the master device and runs as a backup device for the master device. In addition to the stack Master equipment, other devices are Slave equipment. more than one Slave device may exist in the stack .

Advantages of Stacking:

1 simplified management. irf IRF stacking system, This is equivalent to directly logging in to irf in the system master device. through to Master device configuration to manage the entire irf< Span style= "font-family: ' The song Body '; > Stacks and the effects of all devices within the stack without physically connecting to each member device, assigning the member device the ip, connectivity, running routing protocol, etc.

2, high reliability. The high reliability of stacking is manifested in many aspects, such as: The stacking system consists of several member devices,the Master device is responsible for the operation, management and maintenance of the stack,and the Slave device can also handle the business as a backup. once Master equipment failure, the system will quickly and automatically elect new Master , to ensure that the business is not interrupted through the stacking, so that the 1:n backup of the device is realized . In addition, the physical stacking ports between member devices support aggregation, and the physical connection between the stacking system and the upper and lower devices also supports aggregation capabilities, which improves the reliability of the stacking system through multi-link backups.

The life cycle of the entire stack is divided into four stages: physical connection, topology collection, role election, stack management and maintenance .

A leased line can be used between the physical stacking ports, or a normal ethernet cable or fiber connection can be used.

each member device in the stack interacts with a member device that is directly adjacent to itself Hello messages to collect the topological relationships of the entire stack. The Hello message carries topological information, including the stacking port connection relationship, member device number, member device priority, bridge MAC for member devices , and so on.

role elections can occur in the event of topological turbulence, such as stacking builds, new device joins, or stacked splits. the electoral rules for the role are as follows (judging from the first one, if the members of the election are more than optimal, continue to judge the next one until the only best member is found, and the election is stopped.) This optimal member is the stack Master device and the other devices are Slave devices):

(1) The current master priority; (when the stack system is formed, there is no Master device, all joined devices assume that they are masterand will jump to the second rule to continue to compare)

(2) Priority of membership is high;

(3) long system operation time is preferred;

(4) member Bridge MAC address is small priority.

When the device starts, the topology is collected first and participates in the role election. After processing succeeds, the stacking system will not function properly. After the role election is complete, stack management enters the stack maintenance phase.

When a stack link is broken, the original stack may split into two (or more) stacks with exactly the same global configuration, which can cause network failure while running on the network. in order to improve the high availability of the system, when the stack splits we need a mechanism to detect multiple stacks that exist simultaneously in the network, and handle the network to function properly. Multi- Active detection (multi-active Detection, referred to as MAD) is one such detection and processing mechanism.

the device supports two modes of operation: Stacking mode and standalone operation mode.

If the device is currently in stand-alone mode, but needs to be added to the stack, the run mode must be switched to stacking mode to form a stack.

when the device is in stacking mode, even if only one device can form a stack, it also requires some system resources to manage and maintain the stack. Therefore, if the device in the current network does not need to be stacked with another device, it is recommended that the operating mode be configured as stand-alone mode and the device will go back to the stand-alone state.

When switching between operating modes, the device restarts automatically, allowing the new operating mode to take effect. To prevent loss of configuration, save the current configuration before switching modes.

When you identify a device as a member number in a stack, configure the stacking port and priority is also based on the device number, so modifying the device member number may cause the device configuration to change or be lost, so be careful to configure it. For example, after the device is configured for stacking ports, save the configuration, modify the ID, and restart, because the one dimension of the stack port is represented by the member number, so when the device member number changes, the configuration of the stack port is invalidated.

If there is no enable auto-load feature when participating in the stack of device software versions with When the Master device is inconsistent, the newly added or low-priority device does not start correctly. Users are required to manually upgrade the device version and then add the device to the stack. Enable auto-loading, when a member device joins a stack, it is compared to the software version number of the master device and, if not, automatically downloads the boot file from the master device and re-join the stack using the new system boot file restart. If the file name of the newly downloaded startup file is the same as the original file name on the device, the original boot file will be overwritten.

regardless of which method you use to log in to the stack system, you are actually logged in Master equipment. Master is the configuration and control Center for the stacking system, which, when configured on Master , synchronizes these configurations to the Slave device.

References :http://wenku.baidu.com/view/f94b4958312b3169a451a4a1.html(h3c PDF)

Http://www.h3c.com.cn/Products___Technology/Technology/System_Management/Other_technology/Technology_recommend /200904/632642_30003_0.htm(h3c website )

Note: This article is compiled by the author's reference.

This article is from the "Network Diagram" blog, be sure to keep this source http://1234012345.blog.51cto.com/943137/1640721

About Stacking Technology