EtherChannel - Load Balancing on CatOS
In Cisco Catalyst 6500/6000 series switches using the CatOS operating system, load balancing in EtherChannel is achieved through a hashing algorithm that computes a value between 0 and 7. This value determines which specific port in the PortChannel will be used. The load balancing ratios, also known as "masks", depend on the number of ports in the EtherChannel:
- 8 ports: 1:1:1:1:1:1:1:1
- 7 ports: 2:1:1:1:1:1:1
- 6 ports: 2:2:1:1:1:1
- 5 ports: 2:2:2:1:1
- 4 ports: 2:2:2:2
- 3 ports: 3:3:2
- 2 ports: 4:4
CatOS can support up to 8 physical links within a single PortChannel.
Modern devices using Cisco IOS and IOS XE do not use these load balancing masks. Instead, they rely on a hash result of the packet’s header. If a link in an EtherChannel goes down, the traffic is redistributed evenly over the remaining links according to the hash algorithm.
Links:
https://forum.networklessons.com/t/etherchannel-on-cisco-ios-catalyst-switch/1084/186?u=lagapidis
https://www.cisco.com/c/en/us/support/docs/lan-switching/etherchannel/12023-4.html
https://networklessons.com/switching/etherchannel-cisco-ios-catalyst-switch/