Nexus 7000 NXOS 6.x "port-channel load-balance xxxx rotate ## "

[sokarlsson]

Hello!

I can not find a good description on what the option "rotate" really does for port-channel load-balance in N7k. Can someone explain this?

[Reza Sharifi · Accepted solution]

Hi,

here are all the options.

Destination MAC address

•Source MAC address

•Source and destination MAC address

•Destination IP address

•Source IP address

•Source and destination IP address

•Source TCP/UDP port number

•Destination TCP/UDP port number

•Source and destination TCP/UDP port number

http://www.cisco.com/en/US/docs/switches/datacenter/sw/5_x/nx-os/interfaces/configuration/guide/if_portchannel.html

HTH

[sokarlsson]

Yep those are the load balancing options you have but added to that you can have another option which is "rotate ". Here is some output from the switch:

HK-N7k-1(config)# port-channel load-balance src-dst ip-l4port-vlan ?

  fex     FEX devices

  module  Specify a module number

  rotate  Offset the hash-input

HK-N7k-1(config)# port-channel load-balance src-dst ip-l4port-vlan rotate ?

  <0-15>  Offset the hash-input

It's the option in bold I'm interested in. I can not find any good info on what it does/is for.PS: I clocked correct answer by mistake on your answer Reza.

[Lennart Jung]

Hi,

got the same question and found this explanation for the Nexus 9000 (which is possibly transferrable in parts to the Nexus 7000):

The rotate option causes the hash algorithm to rotate the link picking selection so that it does not continually choose the same link across all nodes in the network. It does so by influencing the bit pattern for the hash algorithm. This option shifts the flow from one link to another and load balances the already load-balanced (polarized) traffic from the first ECMP level across multiple links.

http://www.cisco.com/c/en/us/td/docs/switches/datacenter/nexus9000/sw/6-x/unicast/configuration/guide/l3_cli_nxos/l3_manage-routes.html

[vlenis]

the number to use is an option between 0 and 64, how to select the right number?