Link Aggregation Principles
The bandwidth of the logical link is increased by about (n-1) times, where n is the number of aggregated paths. In addition, after aggregation, the reliability is greatly improved, because as long as one of the n links can work normally, this link can work. In addition, link aggregation can achieve load balancing. Because, two (or more) switches (or other network devices) connected together through link aggregation, through internal control, can also reasonably distribute data to the devices connected by aggregation to achieve load sharing. Link aggregation can be divided into manual mode and LACP mode. LACP mode requires the participation of link aggregation control protocol LACP. The advantages of LACP mode are:
1. Increase bandwidth: link aggregation can bundle multiple links into a logical link, and the bandwidth of the bundled link is the sum of the bandwidth of each independent link.
2. Improve reliability: Multiple links in link aggregation are mutual backups. When a link is disconnected, traffic will be automatically redistributed among the remaining links.
3. Provide backup function
Create a topology map
1. Configure link aggregation manual mode
SW1
<Huawei>system-view
[Huawei]undo info-center enable
Info: Information center is disabled.
[Huawei]sysname SW1
Configure the link aggregation group of SW1
[SW1]int Eth-Trunk 10 //创建聚合组序号为10
[SW1-Eth-Trunk10]trunkport GigabitEthernet 0/0/1 to 0/0/3 //把g0/0/1到0/0/3添加到组
Info: This operation may take a few seconds. Please wait for a moment...done.
[SW1-Eth-Trunk10]port link-type trunk //把三个端口设置为Trunk口
[SW1-Eth-Trunk10]port trunk allow-pass vlan all //允许所有的VLAN通过
SW2
<Huawei>system-view
Enter system view, return user view with Ctrl+Z.
[Huawei]sysname SW2
Info: Information center is disabled.
Configure the link aggregation group of SW2
[SW2]int Eth-Trunk 10
[SW2-Eth-Trunk10]trunkport GigabitEthernet 0/0/1 to 0/0/3
Info: This operation may take a few seconds. Please wait for a moment...done.
[SW2-Eth-Trunk10]port link-type trunk
[SW2-Eth-Trunk10]port trunk allow-pass vlan all
Check the Eth-trunk configuration and status on the two switches respectively
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2. Configure link aggregation LACP mode
SW1
[SW1]int Eth-Trunk 10 //Create link aggregation group 10
[SW1-Eth-Trunk10]mode lacp-static //Configure link aggregation mode LACP
[SW1-Eth-Trunk10]trunkport GigabitEthernet 0/0/1 to 0/0/3 //Add g0/0/1-0/0/3 to group
Info: This operation may take a few seconds. Please wait for a moment...done.
[SW1-Eth-Trunk10] quit
SW2
[SW2]int Eth-Trunk 10
[SW2-Eth-Trunk10]mode lacp-static
[SW2-Eth-Trunk10]trunkport GigabitEthernet 0/0/1 to 0/0/3
Info: This operation may take a few seconds. Please wait for a moment...done.
[SW2-Eth-Trunk10]quit
View the configuration and status of the link aggregation group on switch SW1
Set LACP system priority on SW1 and view related information
Modify max active interface on SW1
[SW1-Eth-Trunk10]max active-linknumber 5 //设置最大活动端口数为5
Modify the LACP preemption function on SW1 and check the information
[SW1]int Eth-Trunk 10
[SW1-Eth-Trunk10]lacp preempt enable//enable LACP preemption function
[SW1-Eth-Trunk10]lacp preempt delay 10//preemption delay is 10
[SW1-Eth-Trunk10]quit
Observe the link aggregation status of SW1
Observe the link aggregation status of SW2
Summarize:
| dimension |
manual mode |
LACP mode |
|---|---|---|
| How to establish Eth-Trunk |
The establishment of an Eth-Trunk and the addition of member interfaces are manually configured without the participation of link aggregation control protocols. |
The establishment of Eth-Trunk is based on the LACP protocol. LACP provides a standard negotiation method for devices exchanging data, so that the system can automatically form an aggregated link according to its own configuration and start the aggregated link to send and receive data. After the aggregated link is formed, it is responsible for maintaining the link state. Automatically adjust or dissolve link aggregation when aggregation conditions change. |
| Whether the device needs to support the LACP protocol |
unnecessary |
need |
| data forwarding |
Normally, all links are active links. All active links participate in data forwarding. If an active link fails, the link aggregation group automatically distributes traffic among the remaining active links. |
Normally, some links are active links. All active links participate in data forwarding. If an active link fails, the link aggregation group automatically selects a link among the inactive links as the active link, and the number of links participating in data forwarding remains unchanged. |
| Whether to support cross-device link aggregation |
not support |
support |
| fault detection |
Only limited faults such as disconnection of member links in the same aggregation group can be detected, but faults such as link disconnection and misconnection cannot be detected. |
It can not only detect limited faults such as disconnection of member links in the same aggregation group, but also detect faults such as link faults and link misconnections. |