用交叉网线分别把C2950A交换机的FastEthernetO

用交叉网线分别把C 2950A 交换机的FastEthernetO/23、24端口和C2950B交换机的FastEthernet0/23、24端口连接起来。

图1  交换机的Etherchannel连接

手动配置EtherChannel

⑴ 创建EtherChannel：

C 2950A (config)#interface port-channel 3

⑵ 将物理接口指定到通道中：

C 2950A (config)# interface fa0/23

C 2950A (config-if)#channel-group 3 mode on

此时交换机显示：

00:21:06: %EC-5-BUNDLE: Interface Fa0/23 joined port-channel Po3

00:21:08: %LINK-3-UPDOWN: Interface Port-channel3, changed state to up

00:21:09: %LINEPROTO-5-UPDOWN: Line protocol on Interface Port-channel3, changed state to up

C 2950A (config-if)# interface fa0/24

C 2950A (config-if)# channel-group 3 mode on

00:21:26: %EC-5-BUNDLE: Interface Fa0/24 joined port-channel Po3 

⑶ 在以太通道上启用Trunking：

  C 2950A (config)#interface port-channel 3

C 2950A (config-if)#switchport mode trunk

⑷ 监测EtherChannel的状态：

①C 2950A # show etherchannel 3 summary

Flags:  D - down        P - in port-channel

            I - stand-alone s - suspended

            R - Layer3      S - Layer2

            U - port-channel in use

Group   Port-channel   Ports

-------+--------------+------------------------------------------------

2     Po2(SU)        Fa0/23(P)  Fa0/24(P) 

②C 2950A #show etherchannel 3 brief

Group state = L2

Ports: 2   Maxports = 8

Port-channels: 1 Max Port-channels = 1

 

自动配置EtherChannel

⑴ C 2950A (config)#interface fa0/23

C 2950A (config-if)#channel-group 2 mode desirable

C 2950A (config-if)#switchport mode trunk

此时交换机显示：

Creating a port-channel interface Port-channel2

⑵ C 2950A (config-if)# interface fa0/24

C 2950A (config-if)# channel-group 2 mode desirable

C 2950A (config-if)#switchport mode trunk

 

此时交换机无显示!

⑶ 用show etherchannel 2 summary可以看到channel已存在，但显示接口和Port-channel都处于Down状态。

    C 2950A #show etherchannel 2 summary

Flags:  D - down        P - in port-channel

           I - stand-alone s - suspended

           R - Layer3      S - Layer2

           U - port-channel in use

Group  Port-channel      Ports

--------+--------------------+-----------------------------------------------------------

2      Po2(SD)       Fa0/23(D)  Fa0/24(D) 

    ⑷ 用show running-config显示发现接口23、24均处于关闭状态，用no shutdown命令将接口打开：

    C 2950A (config)#int fa0/23

C 2950A (config-if)#no shut

00:39:38: %LINK-3-UPDOWN: Interface FastEthernet0/23, changed state to up

00:39:40: %LINK-3-UPDOWN: Interface FastEthernet0/23, changed state to up

00:39:41: %DTP-5-TRUNKPORTON: Port Fa0/23 has become dot1q trunk

00:39:43: %EC-5-BUNDLE: Interface Fa0/23 joined port-channel Po2

00:39:44: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan1, changed state to up

00:39:44: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/23, changed state to up

00:39:45: %LINK-3-UPDOWN: Interface Port-channel2, changed state to up

00:39:46: %LINEPROTO-5-UPDOWN: Line protocol on Interface Port-channel2, changed state to up

    C 2950A (config)#int fa0/24

C 2950A (config-if)#no shut

00:40:23: %LINK-3-UPDOWN: Interface FastEthernet0/24, changed state to up

00:40:27: %DTP-5-TRUNKPORTON: Port Fa0/24 has become dot1q trunk

00:40:28: %EC-5-BUNDLE: Interface Fa0/24 joined port-channel Po2

00:40:29: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/24, changed state to up

    可以看到EtherChannel和Trunk都起来了。

    【问题】：为什么自动配置时，接口必须用no shutdown命令打开后EtherChannel和Trunk才能起来，而手动配置时不需要？

    第3步：取消EtherChannel

    ⑴ 分别将端口从EtherChannel中退出：

    C2950B(config)#int fa0/23

C2950B(config-if)#no channel-group 3 mode on

00:47:50: %EC-5-UNBUNDLE: Interface Fa0/23 left the port-channel Po3

C2950B(config-if)#int fa0/24

C2950B(config-if)#no channel-group 3 mode on

00:48:10: %EC-5-UNBUNDLE: Interface Fa0/24 left the port-channel Po3

00:48:11: %LINEPROTO-5-UPDOWN: Line protocol on Interface Port-channel3, changed state to down

00:48:24: %SYS-5-CONFIG_I: Configured from console by console

00:48:57: %DTP-5-NONTRUNKPORTON: Port Fa0/23-Fa0/24 has become non-trunk

00:48:57: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/23, changed state to down

00:48:57: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/24, changed state to down

    ⑵ 直接取消EtherChannel：

C 2950A (config)#no interface port-channel 3

00:31:11: %EC-5-UNBUNDLE: Interface Fa0/23 left the port-channel Po3

00:31:11: %EC-5-UNBUNDLE: Interface Fa0/24 left the port-channel Po3

00:31:12: %DTP-5-NONTRUNKPORTON: Port Fa0/23-Fa0/24 has become non-trunk

00:31:12: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan1, changed state to down

00:31:13: %LINK-5-CHANGED: Interface FastEthernet0/23, changed state to administratively down

00:31:13: %LINK-5-CHANGED: Interface FastEthernet0/24, changed state to administratively down

00:31:14: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/23, changed state to down

00:31:14: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/24, changed state to down