Best etherchannel load balancing for many source to 1 dest?

[CiscoPurpleBelt]

So lets say I have an etherchannel where many hosts talk to 1 server, would source mac load-balancing be the best option?

[Reza Sharifi]

Yes, source MAC is a good option since you have multiple sources and one destination.

HTH

[Andrew Khalil]

Hello @CiscoPurpleBelt,

Greetings,

I would like to say that the word "many hosts talk to a server" is not accurate enough to get an accurate reply,

simply because there are several scenarios of topology that can be described by the same word, but the way of load balance differs! 

Let me explain it in detail, for example, if your hosts are connected to switches and then to a switch finally that is connected to the server, so you can use the source mac address for the load balance as @Reza Sharifi mentioned!

but if there is a router(s) in between the hosts and the server, you mustn't use the source mac address, as the source mac addresses will be the router's one (the last router which is the nearest one to the server) in this case, you will need to use source IP address for load balancing! 

The idea that the switch uses an algorithm according to it, it is choosing the link that will carry the data, and this algorithm is applied to each packet, and according to the load balancing method that you configured, it will use it for that calculation! so if you configured the source mac address, and there is a router, every packet will contain the same mac address, so the results of the calculations will be the same all the time, which means that ONLY one link will be used! 

Happy to help! 

Please, don't forget to rate any helpful reply and to mark solutions!

Bst Rgds,

Andrew Khalil

[Joseph W. Doherty · Accepted solution]

It might, if you're only concerned about traffic from hosts to one server (what about converse traffic flow?) and both hosts and server are in the same L2 domain and your hardware only supports a single L2 attribute. If so, from one server to hosts you would want to use dest-mac. From hosts to server you would want to use src-mac (as you have). The general rule is, you want the hashing attribute(s) to vary.

Except for some real old Cisco switches, you should find most should now support using both src and dest MAC, which can be used in either direction, and most also should now support L3 attributes, such as offering src and dest IP, which works when your also crossing L3 hops (or still within the same network).

Some higher end switches also allow for inclusion of L4 attributes (i.e. port numbers), which can help distribute load when there's multiple application flows between just a pair of hosts.