Netis ST3326(ST-3302) [36/118] Understanding load balancing and forwarding methods

Layer 2 EtherChannels, trunking state, and VLAN numbers.

Interfaces can form an EtherChannel when they are in different LACP modes as long as the

modes are compatible. For example:

 An interface in the active mode can form an EtherChannel with another interface that is in

the active mode.

 An interface in the active mode can form an EtherChannel with another interface in the

passive mode.

An interface in the passive mode cannot form an EtherChannel with another interface that is

also in the passive mode because neither interface starts LACP negotiation.

An interface in the on mode that is added to a port channel is forced to have the same

characteristics as the already existing on mode interfaces in the channel.

Understanding Load Balancing and Forwarding Methods

EtherChannel balances the traffic load across the links in a channel by randomly associating a

newly learned MAC address with one of the links in the channel.

With source-MAC address forwarding, packets forwarded to an EtherChannel are distributed

across the ports in the channel based on the source-MAC address of the incoming packet.

Therefore, to provide load balancing, packets from different hosts use different ports in the

channel, but packets from the same host use the same port in the channel. The MAC address

learned by the switch does not change).

With destination-MAC address forwarding, packets forwarded to an EtherChannel are distributed

across the ports in the channel based on the destination host MAC address of the incoming

packet. Therefore,packets to the same destination are forwarded over the same port, and

packets to a different destination might be sent on a different port in the channel.

Multiple workstations are connected to a switch, and an EtherChannel connects the switch to

the router.

Source-based load balancing is used on the switch end of the EtherChannel to ensure that the

switch efficiently uses the bandwidth of the router by distributing traffic from the workstation

across the physical links. Since the router is a single MAC address device, it uses

destination-based load balancing to efficiently spread the traffic to the workstations across the

physical links in the EtherChannel.