拓扑:
配置需求：
将拓扑中的SW1和SW2的E1/0和E1/1这两个接口捆绑成一个链路。
配置步骤如下：
1、我们在SW1的e1/0-1配置PAgp
SW1(config)#interface range e1/0-1
SW1(config-if-range)#shutdown
SW1(config-if-range)#switchport trunk encapsulation dot1q
SW1(config-if-range)#switchport mode trunk
SW1(config-if-range)#channel-group 1 mode desirable
Creating a port-channel interface Port-channel 1
SW1(config-if-range)#no shutdown
2、我们在SW2的e1/0-1配置PAgp
SW2(config)#int range e1/0-2
SW2(config-if-range)#shutdown
SW2(config-if-range)#switchport trunk encapsulation dot1q
SW2(config-if-range)#switchport mode trunk
SW2(config-if-range)#channel-group 10 mode auto
Creating a port-channel interface Port-channel 10
SW2(config-if-range)#no shutdown
验证如下：
SW2(config)#do show etherchannel summary
Flags: D - down P - bundled in port-channel
I - stand-alone s - suspended
H - Hot-standby (LACP only)
R - Layer3 S - Layer2
U - in use N - not in use, no aggregation
f - failed to allocate aggregator
M - not in use, minimum links not met
m - not in use, port not aggregated due to minimum links not met
u - unsuitable for bundling
w - waiting to be aggregated
d - default port
A - formed by Auto LAG
Number of channel-groups in use: 1
Number of aggregators: 1
Group Port-channel Protocol Ports
------+-------------+-----------+-----------------------------------------------
10 Po10(SU) PAgP Et1/0(P) Et1/1(P) Et1/2(I)
两个接口被捆绑到以太通道组10（本地意义，两端可不相同），S代表是二层，U代表可用，P代表绑定成功。
验证如下：
SW2#show interfaces port-channel 10
Port-channel10 is up, line protocol is up (connected)
Hardware is EtherChannel, address is aabb.cc00.4011 (bia aabb.cc00.4011)
MTU 1500 bytes, BW 20000 Kbit/sec, DLY 1000 usec, //捆绑之后的带宽为20Mbps
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
Keepalive set (10 sec)
Auto-duplex, Auto-speed, media type is unknown
input flow-control is off, output flow-control is unsupported
Members in this channel: Et1/0 Et1/1
ARP type: ARPA, ARP Timeout 04:00:00
Last input 00:00:01, output never, output hang never
Last clearing of "show interface" counters never
Input queue: 0/2000/0/0 (size/max/drops/flushes); Total output drops: 0
Queueing strategy: fifo
Output queue: 0/40 (size/max)
5 minute input rate 1000 bits/sec, 1 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
74 packets input, 6145 bytes, 0 no buffer
Received 66 broadcasts (0 multicasts)
0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
0 input packets with dribble condition detected
82 packets output, 7828 bytes, 0 underruns
0 output errors, 0 collisions, 0 interface resets
0 unknown protocol drops
0 babbles, 0 late collision, 0 deferred
0 lost carrier, 0 no carrier
0 output buffer failures, 0 output buffers swapped out