Overview

Link aggregation is a method of combining multiple physical network links / interfaces into a single logical link known as a Link Aggregation Group (LAG) or bond. Link aggregation helps to increase performance, increases bandwidth and reliability. Link Aggregation also provides load balancing where network traffic across the logical link is distributed over the physical links.

 

In Link Aggregation each port is assigned a unique, globally administered MAC address. Link Aggregation allows a MAC Client to treat a set of one or more links as if it are a single link. A Mac Client communicates with a set of links through an aggregator. Aggregator binds one or more links within a System. It is the responsibility of the Aggregator to distribute traffic from the MAC Client to the various ports and from the ports to the MAC Client. 

 

The following diagrams describe the typical network scenario and how Load balancing and failover can be achieved through link aggregation.


1.  This is a normal scenario where the 100 Mbps bandwidth is equally distributed among the hosts.

This is a normal scenario where the 100 Mbps bandwidth is equally distributed among the hosts.





2. Link aggregation provides load balancing by distributing network traffic across two or more network interface that appear as a single network interface in order to increase reliability through redundancy.

In this scenario the links are aggregated and a bond has been created. Each link has 100 Mbps of bandwidth. As the links are aggregated, the total bandwidth will be 300 Mbps. This bandwidth will be distributed among the hosts, hence now the bandwidth for each host will be increased to 100 Mbps.



3. Similarly fail-over can be achieved by combining two or more network interface. In case one of the network interface fails, the traffic will be automatically directed through the other network interface.

In this scenario when one of the links in the bond fails, the traffic is automatically directed through the other link and the bandwidth of the active link is distributed among the hosts.



In Link Aggregation the modes provide fault tolerance and load balancing benefits. Currently Terminator supports the following modes for Link aggregation:


802.3ad (LACP): IEEE 802.3ad Dynamic link aggregation. Utilizes all slaves (links) in the active aggregator according to the 802.3ad specification. This mode provides load balancing and fault tolerance. This mode requires a switch that supports IEEE 802.3ad LACP.

 

Round Robin: This mode transmits packets in sequential order from the first available slave through the last. This mode provides load balancing and fault tolerance.

 

Xor: In this mode packets are transmitted based on the transmit hash policy. This mode provides load balancing and fault tolerance.

 

Broadcast: This mode transmits everything on all slave interfaces. This mode provides fault tolerance.

 

Active-Backup: Only one slave in the link aggregation interface is active. A different slave becomes active if, and only if, the active slave fails. This mode provides fault tolerance.



How to Configure Link Aggregation


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