Etherchannel load-balance

[Kudetauk77]

Hi all 

I have an Cisco 5525 ASA doing the routing for most of my subnets through subinterfaces that is bundled into a 6 port etherchannel . This connected to a L3 switch with some subnets . This then has L2 switches hanging off it . 

I have noticed the port channel is not load balancing correctly . The ASA is set for src-dst-ip , the L3 switch is set for src-mac , 

How do I decide which to use . I am assuming 

1. They need to match to correctly load balance

2. I can only configure globaaly on the switch 

The layer 3 switch has L2 at one side and the ASA (L3) at the other so which do I chose ? 

Thanks 

Craig

[Bogdan Nita]

Hi Craig,

Having different hashing mechanisms on the end of the port channel is not necessarily incorrect.

Port channel balances the traffic load across the physical links in a channel using the hash to obtain a value that selects one of the physical links in the channel.

In order to optimally balance the traffic the hash needs to have as input values as random as possible.

Because the hash uses a binary pattern the recommended number of links in a port channel are powers of 2: 2,4,8,16...

Because you have a 6 links port channel even if the hash values are random you will not be able to have perfect load balancing (same load on every link).

In practice you could monitor the links and see the load of every link over a period of time, if the difference between the load is to big you can tweak the values used in the hash according to your environment and/or add links to the port channel.

HTH

Bogdan