LACP是什么？基于IEEE802.3ad标准的LACP，英文全称 Link Aggregation Control Protocol， 翻译成中文叫做链路汇聚控制协议，用于实现链路动态汇聚与解汇聚。
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LACP是什么？
基于IEEE802.3ad标准的LACP，英文全称 Link Aggregation Control Protocol， 翻译成中文叫做链路汇聚控制协议，用于实现链路动态汇聚与解汇聚。
LACP通过LACPDU与对端交互信息。DU指Data Unit，数据单元。可以向对端通告MAC地址，优先级，端口号，Key等。对端接收到信息后，通过与其保存的信息进行比较和计算，确定加入或退出某个汇聚组。
主要用来干啥呢？对，汇聚嘛，当然是用来做端口汇聚。还可以做负载分担，链路备份（自动倒换）。
注意，手工配置的负载分担，配置基本的Eth-Trunk接口模式，不需配置LACP，成员接口（selected）都参与数据转发。
配置LACP的话，可以配置成静态或动态。区别在于，静态模式下，成员接口都是手工配置加入，但那些接口是selected，那些是standby的则由LACP协议决定。动态模式下，包括成员接口的加入，活动接口的选择，都是由LACP协议决定，即使说，启动动态LACP的设备不需创建Eth-Trunk接口，也不需要指定接口。
使用LACP协议的时候，Selected和Standby端口都能收发LACPDU， 但standby接口不转发用户报文。
另外，在使用LACP的情况下，无论是静态汇聚还是动态汇聚，看到的standby端口状态是down的。
下面看一下实际案例，
Huawei NE05E G0/2/4及G0/2/5 两个10G口做Trunk与OLT(MA5800X7)组网双上行(0/8/0 1, 0/9/0 1)配置如下：
#NE05E:#interface Eth-Trunk15 portswitch port trunk allow-pass vlan 1 to 100 mode lacp-static load-balance l4#interface GigabitEthernet0/2/4 undo shutdown eth-trunk 15 dcn#interface GigabitEthernet0/2/5 undo shutdown eth-trunk 15 dcn##MA5800X7:[lacp-config] <lacp-config> link-aggregation lacp-key 0/8/0 1 link-aggregation add-member 0/8/0 0/9 0 link-aggregation add-member 0/8/0 0/9 1 link-aggregation add-member 0/8/0 0/9 2 link-aggregation add-member 0/8/0 0/9 3#在MA5800的配置里，实际上display current的时候看不到类似“ link-aggregation add-member 0/8/0 0/9 0” 这些语句，但是可以通过不同命令来查看。 下面“display lacp link-aggregation summary” 可以看到selected端口有2个，standby的有6个，分别对应0/8/0 和0/9/0 和其余6个未selected的端口（其实这些端口都没有物理连接，主要是两个10G口上行就足够了，光模块省点用)
(config)#display lacp link-aggregation summary{ <cr>||<K> }: Command: display lacp link-aggregation summary Actor Priority : 32768 MAC Address: 7858-6000-e7ab Short Period : 1 s Long Period: 30 s Priority Preemption: Disable Timeout : Fast ---------------------------------------------------------------------------- Agg Partner Partner Select Standby Load Backup Master Admin ID Pri MAC Ports Ports Sharing Protect Port Key ---------------------------------------------------------------------------- 1 32768 80b5-75c2-27e5 2 6 YES NO 0 /8 /0 1 ----------------------------------------------------------------------------(config)#display lacp link-aggregation verbose 1{ <cr>||<K> }: Command: display lacp link-aggregation verbose 1 System Priority : 32768 MAC Address : 7858-6000-e7ab Protect Mode : Non-BackupProtect Admin Key : 1 Preempt Delay(s): 0 Master Port: 0/8/0 Actor Port Priority : 16384 Oper-key : 1 Port Role : SELECTED Port Status: C&D Partner System Priority: 32768 MAC Address: 80b5-75c2-27e5 Port Priority : 32768 Oper-key : 3905 Sub Port: 0/9/0 Actor Port Priority : 16384 Oper-key : 1 Port Role : SELECTED Port Status: C&D Partner System Priority: 32768 MAC Address: 80b5-75c2-27e5 Port Priority : 32768 Oper-key : 3905 Sub Port: 0/8/1 Actor Port Priority : 16384 Oper-key : 0 Port Role : STANDBY Port Status: Non-C&D Sub Port: 0/8/2 Actor Port Priority : 16384 Oper-key : 0 Port Role : STANDBY Port Status: Non-C&D Sub Port: 0/8/3 Actor Port Priority : 16384 Oper-key : 0 Port Role : STANDBY Port Status: Non-C&D Sub Port: 0/9/1 Actor Port Priority : 16384 Oper-key : 0 Port Role : STANDBY Port Status: Non-C&D Sub Port: 0/9/2 Actor Port Priority : 16384 Oper-key : 0 Port Role : STANDBY Port Status: Non-C&D Sub Port: 0/9/3 Actor Port Priority : 16384 Oper-key : 0 Port Role : STANDBY Port Status: Non-C&D看一下路由器上的统计：
[~NE05E_01]disp lacp briefSystem Priority: 32768System ID : 80b5-75c2-27e5[~NE05E_01]disp lacp statistics eth-trunk 15 Eth-Trunk15's PDU statistic is: ------------------------------------------------------------------------------- Port LacpRevPdu LacpSentPdu MarkerRevPdu MarkerSentPdu GigabitEthernet0/2/4 764414 23278073 0 0 GigabitEthernet0/2/5 764422 23278081 0 0[~NE05E_01]disp int Eth-Trunk 15Eth-Trunk15 current state : UP (ifindex: 38)Line protocol current state : UPLink quality grade : GOODDescription:Switch Port, TPID : 8100(Hex), Hash arithmetic : According to flow,Maximal BW: 20Gbps, Current BW: 20Gbps, The Maximum Transmit Unit(L3) is 1500 bytesInternet protocol processing : disabledIP Sending Frames' Format is PKTFMT_ETHNT_2, Hardware address is 80b5-75c2-27e5Current system time: 2019-05-17 23:11:49Physical is ETH_TRUNK Last 300 seconds input rate 817341 bits/sec, 914 packets/sec Last 300 seconds output rate 23899360 bits/sec, 2080 packets/sec Input: 2349976240 packets,344045983992 bytes 2308742671 unicast,39406270 broadcast,1827299 multicast 0 errors,0 drops Output:5942717725 packets,8154570342640 bytes 5814368771 unicast,77054633 broadcast,51294321 multicast 0 errors,0 drops Last 300 seconds input utility rate: 0.01% Last 300 seconds output utility rate: 0.11%----------------------------------------------------------PortName Status Weight----------------------------------------------------------GigabitEthernet0/2/4 UP 1GigabitEthernet0/2/5 UP 1----------------------------------------------------------The Number of Ports in Trunk : 2The Number of UP Ports in Trunk : 2[~NE05E_01]disp eth-trunk 15Eth-Trunk15's state information is:Local:LAG ID: 15 WorkingMode: STATICPreempt Delay: Disabled Hash arithmetic: According to flowSystem Priority: 32768 System ID: 80b5-75c2-27e5Least Active-linknumber: 1 Max Active-linknumber: 8Operate status: up Number Of Up Ports In Trunk: 2Timeout Period: Slow--------------------------------------------------------------------------------ActorPortName Status PortType PortPri PortNo PortKey PortState WeightGigabitEthernet0/2/4 Selected 10GE 32768 1 3905 10111100 1GigabitEthernet0/2/5 Selected 10GE 32768 2 3905 10111100 1Partner:--------------------------------------------------------------------------------ActorPortName SysPri SystemID PortPri PortNo PortKey PortStateGigabitEthernet0/2/4 32768 7858-6000-e7ab 16384 1 1 11111100GigabitEthernet0/2/5 32768 7858-6000-e7ab 16384 5 1 11111100我做了链路测试一切正常，细节不说了。
顺便说一下，我这还有一些Adtran OLT TA5000系列，双主控板上行链路汇聚叫做Cross-slot LAG, 配置如下(配置lag的时候要看当前主用板是那块，1/A就用下面模板，1/B的话相应修改）：
interface ten-gigabit-ethernet 1/A/1 lacp mode active no shutdown exitinterface ten-gigabit-ethernet 1/B/1 lacp mode active no shutdown exitlacp response-mode 1/A interactiveinterface lag-group 1/A/1 cross-slot alias "LAG1" link ten-gigabit-ethernet 1/A/1 link ten-gigabit-ethernet 1/B/1 active-links-minimum 1 no shutdown exitno ethernet default interfaceethernet default interface lag-group LAG1查看状态：
OL02-EAS-LON#sh int laglag-group 1/B/1 is IS And up Alias : LAG1 Cross-Slot : enabled Minimum Active Links : 1 Active Links : 2 Link : ten-gig-eth 1/B/1 (UP) Link : ten-gig-eth 1/A/1 (UP)