load balancing etherchannel

Etherchannel is an extremely effective feature providing you with redundancy and load distribution in your switching network. However failing to find the right etherchannel load balance distribution formula my make you under utilizing your network assets.

We will evaluate how you can choose the burden balancing method depending on positioning of switch and traffic type that should be load distributed. I’ll base the discussion on traffic direction from LAN1 to LAN2 but same rules apply within the other direction.


First of all we have to briefly consider how packets are submitted from LAN1 to LAN2

PC1: 192.168.1.2 in LAN1 is pinging PC3: 192.168.2.2 in LAN2

PC1 notice that PC3 is within another subnet (packets have to be delivered to the gateway) therefore it produces a packet using the following information:

Src IP: PC1 Ip - Dst IP: PC3 Ip - Src MAC: PC1 MAC - Dst MAC: R1(GW) .

R1 receives the packet finds a match in the routing table (dst: 192.168.2.2) pointing to another hop (R2) and forwards the packet using the following information:

Src address: PC1 IP - Dst address: PC3 IP - Src MAC: R1 MAC - Dst MAC: R2 Mac.

R2 receives the packet looks up for that destination in the routing table and forwards the packet to PC3 while using following infromation:

Src address: PC1 IP - Dst address: PC3 IP - Src MAC: R2 MAC - Dst MAC: PC3 Mac.

The part that means something us this is actually the sending from R1 to R2 passing with the Etherchannel link between switch1 and switch2 the frame has R1 and R2 MAC addresses as source and destination with respect to the direction from the traffic.

EtherChannel Load balancing techniques:

dst-ip-Load distribution is dependant on the destination-host Ip.

dst-mac-Load distribution in line with the destination-host MAC address from the incoming packet.

src-dst-ip-Load distribution is dependant on the origin-and-destination host-Ip.

src-dst-mac-Load distribution is dependant on the origin-and-destination host-MAC address.

src-ip-Load distribution is dependant on the origin-host Ip.

src-mac-Load distribution is dependant on the origin-MAC address from the incoming packet.

So, What's the best load balancing etherchannel method that meets our situation?

Within our situation its obvious that packets acquired from LAN1 determined to LAN2 may have source Insolvency practitioners of Computers owned by LAN1 and locations of Computers owned by LAN2 but will invariably have R1 MAC address like a source MAC address and R2 like a destination MAC address when passing the switching portion of our topology.

This analysis implies that load distribution techniques based MAC addresses won't supply the best distribution of traffic within the Etherchannel.

We have to consider load distribution depending on IP addresses, but which really provides for us the very best even distribution within the Ehterchannel links?

To reply to this we have to think about the traffic pattern between your two LANs allows begin to see the situations below:

Scenario1: Visitors are random from the workstation to a different meaning any user from LAN1 might be interacting with any user from LAN2. Any IP based load distribution method is going to do the job.

Scenario2: If your server exist (i.e. mail server) most of the two subnets and several Computers will always be delivering or receving visitors to or out of this server only then do we remain with one option providing you with probably the most evenly distribution the src-dst-ip-Load distribution.