本文转自：https://blog.51cto.com/cisco130/1228744

在2块HWIC-4ESW之间,一定要用一根网线连接起来，否则,VLAN无法使用，切记！

这次在一台路由器上配备了两块HWIC-4ESW，开始时没有注意，根本没法用这两块以太网交换模块，搞得自己很紧张，以为碰到不良总代，出了O货，后来到官网上查了一下，原来还有这么一说，算是思科的一个小小硬伤吧，为什么不在机框总线里把这个问题处理好，却一定要在外面飞线呢？

看来思科每次在嘲笑华为时，应该摸下自己的脸是否有点红了。

思科官方的文档：
Configuring Stacking
Stacking is the connection of two switch modules resident in the same chassis so that they behave as a single switch. When a chassis is populated with two switch modules, the user must configure both of them to operate in stacked mode. This is done by selecting one port from each switch module and configuring it to be a stacking partner. The user must then connect with a cable the stacking partners from each switch module to physically stack the switch modules. Any one port in a switch module can be designated as the stacking partner for that switch module.

Beginning in privileged EXEC mode, follow these steps to configure a pair of ports on two different switch modules as stacking partners.

SUMMARY STEPS
1. interface fastethernet interface-id

2. no shutdown

3. switchport stacking-partner interface FastEthernet partner-interface-id

4. exit

5. interface fastethernet partner-interface-id

6. no shutdown

7. end

DETAILED STEPS
Command Purpose
Step 1
Router(config)#interface fastethernet
interface-id
Selects the interface to configure.

Step 2
Router(config-if)#no shutdown
Activates the interface. (Required only if you shut down the interface.)

Step 3
Router(config-if)#switchport
stacking-partner interface FastEthernet
partner-interface-id
Selects and configures the stacking partner port.

Step 4
Router(config-if)#exit
Exits interface configuration mode.

Step 5
Router(config)#interface fastethernet
partner-interface-id
Selects the stacking partner interface.

Step 6
Router(config-if)#no shutdown
Activates the stacking partner interface.

Step 7
Router(config-if)#end
Exits configuration mode.