Hi, everyone! Today I’m going to introduce an example for Configuring Link Aggregation in LACP Mode When Switches Are Directly Connected
Overview
Ethernet link aggregation increases link bandwidth by bundling multiple physical links to form a logical link. Link aggregation can work in manual mode or Link Aggregation Control Protocol (LACP) mode.
If a high link bandwidth between two directly connected devices is required and devices support LACP, the LACP mode is recommended. The LACP mode increases bandwidth, improves reliability, implements load balancing, enhances Eth-Trunk fault tolerance, and provides backup.
In LACP mode, some links are active links and other links are backup links. All the active links participate in data forwarding. If an active link becomes faulty, a backup link is selected to replace the faulty link. That is, the number of links participating in data forwarding remains unchanged.
Configuration Notes
Member interfaces of an Eth-Trunk must use the same Ethernet type and rate.
Both devices of the Eth-Trunk must use the same number of physical interfaces, interface rate, duplex mode, and flow control mode.
If an interface of the local device is added to an Eth-Trunk, an interface of the remote device directly connected to the interface of the local device must also be added to an Eth-Trunk. Otherwise, the two ends cannot communicate.
Both devices of an Eth-Trunk must use the same link aggregation mode.
This example applies to all versions of all S series switches.
Networking Requirements
In Figure 6-6, SwitchA and SwitchB connect to devices in VLAN 10 and VLAN 20 through Ethernet links, and heavy traffic is transmitted between SwitchA and SwitchB. The link between SwitchA and SwitchB is required to provide high bandwidth to implement inter-VLAN communication. Link aggregation in LACP mode is configured on SwitchA and SwitchB to improve the bandwidth and reliability. The following requirements must be met:
Two active links implement load balancing.
One link functions as the backup link. When a fault occurs on an active link, the backup link replaces the faulty link to maintain reliable data transmission.
Devices in the same VLAN can communicate.

Configuration Roadmap
The configuration roadmap is as follows:
Create an Eth-Trunk and configure the Eth-Trunk to work in LACP mode to implement link aggregation.
Add member interfaces to the Eth-Trunk.
Set the LACP system priority and determine the Actor so that the Partner selects active interfaces based on the Actor interface priority.
Set the upper threshold for the number of active interfaces to improve reliability.
Set LACP interface priorities and determine active interfaces so that interfaces with higher priorities are selected as active interfaces.
Create VLANs and add interfaces to the VLANs.
Procedure
Create Eth-Trunk 1 on SwitchA and configure Eth-Trunk 1 to work in LACP mode. The configuration of SwitchB is similar to that of SwitchA, and is not mentioned here.
<HUAWEI> system-view[HUAWEI] sysname SwitchA[SwitchA] interface eth-trunk 1 //Create Eth-Trunk 1.[SwitchA-Eth-Trunk1] mode lacp //Configure link aggregation in LACP mode.[SwitchA-Eth-Trunk1] quit
Add member interfaces to Eth-Trunk 1 on SwitchA. The configuration of SwitchB is similar to that of SwitchA, and is not mentioned here.
[SwitchA] interface gigabitethernet 0/0/1[SwitchA-GigabitEthernet0/0/1] eth-trunk 1 //Add GE0/0/1 to Eth-Trunk 1.[SwitchA-GigabitEthernet0/0/1] quit[SwitchA] interface gigabitethernet 0/0/2[SwitchA-GigabitEthernet0/0/2] eth-trunk 1 //Add GE0/0/2 to Eth-Trunk 1.[SwitchA-GigabitEthernet0/0/2] quit[SwitchA] interface gigabitethernet 0/0/3[SwitchA-GigabitEthernet0/0/3] eth-trunk 1 //Add GE0/0/3 to Eth-Trunk 1.[SwitchA-GigabitEthernet0/0/3] quit
Set the system LACP priority of SwitchA to 100 so that SwitchA becomes the Actor.
[SwitchA] lacp priority 100 //The default system LACP priority is 32768. Change the LACP priority of SwitchA to be higher than that of SwitchB so that SwitchA functions as the Actor.
On SwitchA, set the upper threshold for the number of active interfaces to 2.
[SwitchA] interface eth-trunk 1[SwitchA-Eth-Trunk1] max active-linknumber 2 //The default upper threshold for the number of active interfaces in the LAG is 8. Change the upper threshold for the number of active interfaces to 2.[SwitchA-Eth-Trunk1] quit
Set the interface LACP priority and determine active links on SwitchA.
[SwitchA] interface gigabitethernet 0/0/1[SwitchA-GigabitEthernet0/0/1] lacp priority 100 //The default interface LACP priority is 32768. Change the LACP priority of GE0/0/1 to 100 so that GE0/0/1 serves as the active interface.[SwitchA-GigabitEthernet0/0/1] quit[SwitchA] interface gigabitethernet 0/0/2[SwitchA-GigabitEthernet0/0/2] lacp priority 100 //The default interface LACP priority is 32768. Change the LACP priority of GE0/0/2 to 100 so that GE0/0/2 serves as the active interface.[SwitchA-GigabitEthernet0/0/2] quit
Create VLANs and add interfaces to the VLANs.
# Create VLAN 10 and VLAN 20 and add interfaces to them. The configuration of SwitchB is similar to the configuration of SwitchA, and is not mentioned here.
[SwitchA] vlan batch 10 20[SwitchA] interface gigabitethernet 0/0/4[SwitchA-GigabitEthernet0/0/4] port link-type trunk //Configure the interface as a trunk interface. The default link type of an interface is not trunk.[SwitchA-GigabitEthernet0/0/4] port trunk allow-pass vlan 10[SwitchA-GigabitEthernet0/0/4] quit[SwitchA] interface gigabitethernet 0/0/5[SwitchA-GigabitEthernet0/0/5] port link-type trunk //Configure the interface as a trunk interface. The default link type of an interface is not trunk.[SwitchA-GigabitEthernet0/0/5] port trunk allow-pass vlan 20[SwitchA-GigabitEthernet0/0/5] quit
# Configure Eth-Trunk 1 to allow packets from VLAN 10 and VLAN 20 to pass through. The configuration of SwitchB is similar to the configuration of SwitchA, and is not mentioned here.
[SwitchA] interface eth-trunk 1[SwitchA-Eth-Trunk1] port link-type trunk //Configure the interface as a trunk interface. The default link type of an interface is not trunk.[SwitchA-Eth-Trunk1] port trunk allow-pass vlan 10 20[SwitchA-Eth-Trunk1] quit
Verify the configuration.
# Check information about the Eth-Trunk on each Switch and check whether link negotiation is successful.
[SwitchA] display eth-trunk 1Eth-Trunk1's state information is: Local: LAG ID: 1 WorkingMode: LACP Preempt Delay: Disabled Hash arithmetic: According to SIP-XOR-DIP System Priority: 100 System ID: 00e0-fca8-0417Least Active-linknumber: 1 Max Active-linknumber: 2 Operate status: up Number Of Up Port In Trunk: 2 -------------------------------------------------------------------------------- ActorPortName Status PortType PortPri PortNo PortKey PortState WeightGigabitEthernet0/0/1 Selected 1GE 100 6145 2865 11111100 1GigabitEthernet0/0/2 Selected 1GE 100 6146 2865 11111100 1GigabitEthernet0/0/3 Unselect 1GE 32768 6147 2865 11100000 1 Partner: -------------------------------------------------------------------------------- ActorPortName SysPri SystemID PortPri PortNo PortKey PortStateGigabitEthernet0/0/1 32768 00e0-fca6-7f85 32768 6145 2609 11111100GigabitEthernet0/0/2 32768 00e0-fca6-7f85 32768 6146 2609 11111100GigabitEthernet0/0/3 32768 00e0-fca6-7f85 32768 6147 2609 11110000
[SwitchB] display eth-trunk 1Eth-Trunk1's state information is: Local: LAG ID: 1 WorkingMode: LACPPreempt Delay: Disabled Hash arithmetic: According to SIP-XOR-DIP System Priority: 32768 System ID: 00e0-fca6-7f85Least Active-linknumber: 1 Max Active-linknumber: 8Operate status: up Number Of Up Port In Trunk: 2 -------------------------------------------------------------------------------- ActorPortName Status PortType PortPri PortNo PortKey PortState WeightGigabitEthernet0/0/1 Selected 1GE 32768 6145 2609 11111100 1GigabitEthernet0/0/2 Selected 1GE 32768 6146 2609 11111100 1GigabitEthernet0/0/3 Unselect 1GE 32768 6147 2609 11110000 1 Partner: -------------------------------------------------------------------------------- ActorPortName SysPri SystemID PortPri PortNo PortKey PortStateGigabitEthernet0/0/1 100 00e0-fca8-0417 100 6145 2865 11111100GigabitEthernet0/0/2 100 00e0-fca8-0417 100 6146 2865 11111100GigabitEthernet0/0/3 100 00e0-fca8-0417 32768 6147 2865 11100000
The preceding information shows that the system LACP priority of SwitchA is 100 and is higher than the system LACP priority of SwitchB. GigabitEthernet0/0/1 and GigabitEthernet0/0/2 are active interfaces and are in Selected state. GigabitEthernet0/0/3 is in Unselect state. In addition, load balancing and redundancy are implemented.
Configuration Files
SwitchA configuration file
# sysname SwitchA # vlan batch 10 20 # lacp priority 100 # interface Eth-Trunk1 port link-type trunk port trunk allow-pass vlan 10 20 mode lacp max active-linknumber 2# interface GigabitEthernet0/0/1 eth-trunk 1 lacp priority 100 # interface GigabitEthernet0/0/2 eth-trunk 1 lacp priority 100 # interface GigabitEthernet0/0/3 eth-trunk 1 # interface GigabitEthernet0/0/4 port link-type trunk port trunk allow-pass vlan 10 # interface GigabitEthernet0/0/5 port link-type trunk port trunk allow-pass vlan 20 # return
SwitchB configuration file
# sysname SwitchB # vlan batch 10 20 # interface Eth-Trunk1 port link-type trunk port trunk allow-pass vlan 10 20 mode lacp# interface GigabitEthernet0/0/1 eth-trunk 1 # interface GigabitEthernet0/0/2 eth-trunk 1 # interface GigabitEthernet0/0/3 eth-trunk 1 # interface GigabitEthernet0/0/4 port link-type trunk port trunk allow-pass vlan 10 # interface GigabitEthernet0/0/5 port link-type trunk port trunk allow-pass vlan 20 # return
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