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思科智能堆叠技术概述 Stackwise是一种交换机堆叠技术。独立的多个交换机智能的加入、以一个32Gbps的转发速率加入堆叠互联。它会创建一个交换单元，其配置和路由信息在堆叠交换机之间共享。从一个工作的堆叠中增加或者删除交换机并不影响性能。 Cisco StackWise technology provides an innovative new method for collectively utilizing the capabilities of a stack of switches. Individual switches intelligently join to create a single switching unit with a 32-Gbps switching stack interconnect. Configuration and routing information is shared by every switch in the stack, creating a single switching unit. Switches can be added to and deleted from a working stack without affecting performance. The switches are united into a single logical unit using special stack interconnect cables that create a bidirectional closed-loop path. This bidirectional path acts as a switch fabric for all the connected switches. Network topology and routing information is updated continuously through the stack interconnect. All stack members have full access to the stack interconnect bandwidth. The stack is managed as a single unit by a master switch, which is elected from one of the stack member switches. Each switch in the stack has the capability to behave as a master or subordinate (member) in the hierarchy. The master switch is elected and serves as the control center for the stack. Both the master member switches act as forwarding processors. Each switch is assigned a number. Up to nine separate switches can be joined together. The stack can have switches added and removed without affecting stack performance. 多个交换机通过特定的互联线缆（该线缆为一个双向的无环路径）被统一到一个单独的逻辑交换单元。这个双向的路径扮演了所有互联交换机的交换矩阵。网络拓扑换个路由信息通过堆叠互联不停歇的共享，智能堆叠通过主交换机来管理，当然主交换机通过堆叠成员选举得到 Online Stack Adds and Removals Switches can be added and deleted to a working stack without affecting stack performance. When a new switch is added, the master switch automatically configures the unit with the currently running Cisco IOS ? Software image and configuration of the stack. The stack will gather information such as switching table information and update the MAC tables as new addresses are learned. The network manager does not have to do anything to bring up the switch before it is ready to operate. Similarly, switches can be removed from a working stack without any operational effect on the remaining switches. When the stack discovers that a series of ports is no longer present, it will update this information without affecting forwarding or routing. 在线的堆叠和移除 在一个正在工作的交换机堆叠中增加或者删除交换机并不影响堆叠的性能。当一个新的交换机被增加时，主交换机自动的配置当前的running运行的配置，堆叠将会收集诸如交换表信息和更新MAC地址表，网管人员不需要做任何事情来打破当前的正在进行的操作，类似的交换机也可以从堆叠中移除。 Master Switch Election The stack behaves as a single switching unit that is managed by a master switch elected from one of the member switches. The master switch automatically creates and updates all the switching and optional routing tables. Any member of the stack can become the master switch. Upon installation, or reboot of the entire stack, an election process occurs among the switches in the stack. There is a hierarchy of selection criteria for the election. 1. User priority - The network manager can select a switch to be master. 2. Hardware and software priority - This will default to the unit with the most extensive feature set. The Cisco Catalyst 3750 IP Services (IPS) image has the highest priority, followed by Cisco Catalyst 3750 switches with IP Base Software Image (IPB). Catalyst 3750-E and Catalyst 3750-X run the Universal Image. The feature set on the universal image is determined by the purchased license. The "show version" command will list operating license level for each switch member in the stack. 3. Default configuration - If a switch has preexisting configuration information, it will take precedence over switches that have not been configured. 4. Uptime - The switch that has been running the longest is selected. 5. MAC address - Each switch reports its MAC address to all its neighbors for comparison. The switch with the lowest MAC address is selected. 主交换机选举机制： 1.用户优先级，网管人员来选择一个交换机成为master 2.硬件和软件优先级，这是被广泛使用的方式，3750 IP service的IOS拥有最高优先级，然后为3750 IP base版本的IOS 3750E和3750X运行通用版本的IOS，那么其特性集被购买的License决定 3.默认的配置 如果一个交换机先前已经存在配置信息，那么它将具备相比没有配置交换的更高的优先级 4.运行时间 运行时间最长的交换机被选举为Master设备 5.MAC地址 邻居之间相互报告和对比MAC地址，拥有最低MAC的设备成为Master设备 |
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