What are the three methods of link aggregation?

The three methods of link aggregation in load balancing are manual load sharing mode link aggregation, static LACP mode link aggregation, and dynamic LACP mode link aggregation. Among them, manual load balancing mode is the most basic link aggregation method.

#The operating environment of this article: windows10 system, thinkpad t480 computer.

Three modes of link aggregation in load balancing:

Manual load sharing mode link aggregation

1. Overview of manual aggregation

Manual load balancing mode is the most basic link aggregation method. In this mode, the establishment of the Eth-Trunk interface and the addition of member interfaces are completely configured manually, without the participation of the link aggregation control protocol. In this mode, all member interfaces (selected) participate in data forwarding and share load traffic, so it is called manual load balancing mode. The LACP protocol of manual aggregation ports is closed, and users are prohibited from enabling the LACP protocol of manual aggregation ports.

2. Port status in manual aggregation group

In manual aggregation group, the port may be in two states: Selected or Standby. The port in the Selected state with the smallest port number is the master port of the aggregation group, and the other ports in the Selected state are member ports of the aggregation group.

Since the maximum number of ports in the aggregation group that the device can support is limited, if the number of ports in the Selected state exceeds the maximum number of ports in the aggregation group that the device can support, the system will increase the number of ports in the aggregation group based on the port number. In a large order, some ports are Selected ports and others are Standby ports.

3. Requirements for port configuration for manual aggregation

Generally, manual aggregation does not impose restrictions on the port speed and duplex mode before aggregation. However, the system will perform special processing for the following situations: For ports that are initially in the DOWN state, there is no limit on the port rate and duplex mode during aggregation;

For ports that were once in the UP state, and negotiate or force The port speed and duplex mode have been specified, and the port currently in the DOWN state is required to have the same speed and duplex mode during aggregation; for an aggregation group, when the speed and duplex mode of a port in the aggregation group change, The system does not perform deaggregation, and the ports in the aggregation group are in normal working status. However, if the rate of the main port decreases and the duplex mode changes, packet loss may occur in the forwarding of the port.

LACP Protocol Link Aggregation

LACP (Link Aggregation Control Protocol) link aggregation includes two types:

1) Static LACP mode link Road aggregation

a) Introduction to link aggregation in static LACP mode

In static LACP mode, the establishment of the Eth-Trunk interface and the addition of member interfaces are all completed by manual configuration. However, what is different from link aggregation in manual load balancing mode is that in this mode, LACP protocol packets participate in the selection of active interfaces. That is to say, when a group of interfaces is added to an Eth-Trunk interface, which interfaces among these member interfaces will be used as active interfaces and which interfaces will be used as inactive interfaces need to be determined through negotiation using LACP protocol messages.

The LACP protocol of the static aggregation port is enabled. When a static aggregation group is deleted, its member ports will form one or more dynamic LACP aggregations and keep LACP enabled. Users are prohibited from turning off the LACP protocol of static aggregation ports.

b)Port status in static aggregation group

In a static aggregation group, a port may be in two states: Selected or Standby. Both the Selected port and the Standby port can send and receive the LACP protocol, but the Standby port cannot forward user packets.

2)Dynamic LACP mode link aggregation

a)Dynamic LACP mode link aggregation introduction

In dynamic LACP mode, the establishment of Eth-Trunk interface, the member interface To join, the selection of active interfaces is completed entirely through negotiation through the LACP protocol. This means that for two directly connected devices with the dynamic LACP protocol enabled, there is no need to create an Eth-Trunk interface or specify which interfaces serve as aggregation group member interfaces. The two devices will automatically complete link aggregation through LACP negotiation. operate. Dynamic LACP aggregation is a type of aggregation automatically created/deleted by the system. Users are not allowed to add or delete member ports in the dynamic LACP aggregation. Only ports with the same speed and duplex attributes, connected to the same device, and the same basic configuration can be dynamically aggregated together. Dynamic aggregation can be created even with only one port, which is a single-port aggregation. In dynamic aggregation, the LACP protocol of the port is enabled.

b)Port status in dynamic aggregation group

In a dynamic aggregation group, a port may be in two states: Selected or Standby. Both the Selected port and the Standby port can send and receive the LACP protocol, but the Standby port cannot forward user packets. Since there is a limit to the maximum number of ports in an aggregation group that the device can support, if the current number of member ports exceeds the limit of the maximum number of ports, the local system and the peer system will negotiate to select the optimal port based on the device ID. The size of the ID determines the status of the port. The specific negotiation steps are as follows:

Compare device ID (system priority system MAC address). Compare the system priorities first, and then compare the system MAC addresses if they are the same. The one with the smaller device ID is considered better.

Compare port ID (port priority port number). For each port on the end with the best device ID, first compare the port priorities, and then compare the port numbers if the priorities are the same. The port with the smallest port ID is the Selected port, and the remaining ports are the Standby port. In an aggregation group, the port in the Selected state with the smallest port number is the main port of the aggregation group, and the other ports in the Selected state are member ports of the aggregation group.

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