3550支持3层和2层链路聚合，支持协议lacp（IEEE）和pagp（思科私有）；而2950只支持pagp。故只能使用pagp.在配置2层链路聚合时候，组成port-channel接口的以太口下配置都得一致。

配置命令：

================================
3550：

enable
conf t
int range f0/9 - 10
no shut
switchport mode trunk encapsulation dot1q
switch mode trunk allow vlan add 100,10-13
channel-protocol pagp <pagp/lacp>
channel-group 1 mode on <1-64>
exit
interface port-channel 1
no shutdown
switchport mode trunk encapsulation dot1q
switchport trunk allow vlan 100,10-13
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2950:

en conf t int range f0/9 - 10 no shut switchport mode trunk encapsulation dot1q switch mode trunk allow vlan add 100,10-13 channel-protocol pagp <pagp/lacp> channel-group 1 mode on<1-6> exit interface port-channel 1 no shutdown switchport mode trunk encapsulation dot1q switchport trunk allow vlan 100,10-13