Qtech QSW-2900-24T-AC [59/209] Approaches to link aggregation

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the current channel grou. If transferring to other channel group, only one packet will be transferred.

If there are members in the channel group, this channel group cannot be deleted. Delete interface members

first.

Influence on choosing link redundancy caused by LACP system and interface priority. LACP provides link

redundancy mechanism which needs to guarantee the redundancy consistency of two interconnected switches and

user can configure redundancy link which is realized by system and interface priority. The redundancy choosing

follows the following steps:

First, determine which switch is the choosing standard. For LACP packets interaction, each of the two

switches knows each other’s LACP system priority and system MAC and compares the LACP system priority to

choose the smaller one; if the system priority is the same, compare MAC and choose the smaller one.

Then, choose redundancy link according to the interface parameter of the chosen switch. Compare interface

LACP priority, and choose the inferior one to be redundant. If the priorities are the same, choose the interface whose

interface number is larger to be redundant.

Link aggregation aggregates multiple physical Ethernet ports into one logical link, also called a logical group,

to increase reliability and bandwidth.

3.4.2 LACP

The link aggregation control protocol (LACP) is defined in IEEE 802.3ad. Link aggregation control protocol

data unit (LACPDU) is used for exchanging information among LACP-enabled devices.

After LACP is enabled on a port, the port sends LACPDUs to notify the remote system of its system LACP

priority, system MAC address, port LACP priority, port number, and operational key. Upon receipt of an LACPDU,

the remote system compares the received information with the information received on other ports to determine the

ports that can operate as selected ports. This allows the two systems to reach agreement on the states of the related

ports

When aggregating ports, link aggregation control automatically assigns each port an operational key based on

its rate, duplex mode, and other basic configurations. In an LACP aggregation group, all ports share the same

operational key; in a manual or static LACP aggregation, the selected ports share the same operational key.

3.5 Approaches to Link Aggregation

3.5.1 Manual Link Aggregation

a) Overview

Manual aggregations are created manually. Member ports in a manual aggregation are LACP-disabled.

b) Port states in a manual aggregation

In a manual aggregation group, ports are either selected or unselected. Selected ports can receive and transmit

data frames whereas unselected ones cannot. Among all selected ports, the one with the lowest port number is the

master port and others are member ports.

When setting the state of ports in a manual aggregation group, the system considers the following:

· Select a port from the ports in up state, if any, in the order of full duplex/high speed, full duplex/low

speed, half duplex/high speed, and half duplex/low speed, with the full duplex/high speed being the

most preferred. If two ports with the same duplex mode/speed pair are present, the one with the lower

port number wins out. Then, place those ports in up state with the same speed/duplex pair, link state and

basic configuration in selected state and all others in unselected state.

· When all ports in the group are down, select the port with the lowest port number as the master port

and set all ports (including the master) in unselected state.