A technical principle
1) port aggregation (also called link aggregation), a plurality of ports on the switch are connected physically, logically tied together to form a broadband port has a large, load balancing can be achieved and providing redundant links
2) using EtherChannel port aggregation characteristic, high-speed connections between switches in the switch to provide redundancy. The plurality of FastEthernet or GigabitEthernet physical link between two devices tied together to form a logical link between a device to enhance the bandwidth, provide redundancy.
3 rate) to the computer two switches are 100M, 100M, although two physical channels are connected between SW1 and SW2, the spanning tree may be due, 100M available only link between the switch is easy to form the bottleneck, use port polymerization techniques, the two link aggregation 100M to 200M of a logical link, when a link fails, another link will continue to operate.
Port Aggregation configuration commands in global configuration mode:
interface Range port_num1 to port_num2
Switchport MODE Trunk
Channel Add-Link Group 1 Group 1 MODE ON and turn
Switch # show etherchannel summary: displaying information related to the link aggregation group;
parameters:
port_num1: polymerization start port;
port_num2: polymerizable end port;
Trunk: represents Vlan port can forward all packets, trunk mode interface can simultaneously transmit a plurality of VLAN information;
Trunk two MODE SWITCH and ROUTER, SWITCH and SWITCH between common;
Channel -group: the two or more physical ports grouped together into a logical link, but also the formation of a logical port-Channel port
switchport access MODE: directly connected to the host interface in the VLAN, are access
Two experimental environment (the experiments do Next, two switches in the middle of a cable pay more)
Configuration sw1, sw2, f1 / 3 -4 port and a trunk port aggregation
Three experimental tests
first with regular ping PC6 PC5 then SW1 f1 / 3-port off (shutdown command)
The SW1 f1 / 3 port closing 
this normal communication time PC5 and PC6