Understanding Portchannels on Nexus 7000

[Michael Wingender]

Hi all,

I have a question regarding Loadbalancing on port channels with multiple links and understanding the default behaviour on a Nexus 7000

Here I can read:

"The default load-balancing mode for Layer 3 interfaces is the source and destination IP address, and the default load-balancing mode for non-IP interfaces is the source and destination MAC address."

For me this sounds like: If you use a Layer3 portchannel the decision of which link will be used is calculated based on source and destination IPs. If you define the portchannel as L2 only the decision is made based on MAC addresses only. (Both of course in unchanged default behaviour.)

Now in another document here I can read:

show port-channel load-balance Field Descriptions

Field	Description
System	The load-balancing method configured on the switch.
Non-IP	The field that will be used to calculate the hash value for non-IP traffic.
IP	The fileds used for IPv4 and IPv6 traffic.

This sounds for me like the decision is not made on whether the portchannel is configured as L2 or L3 but it is looking at the ethernet frame and the descision is made based on whether IP or non IP is encapsulated within the frame.

Can somebody clarify?

Br

Michael

[Madhukrishnan Gopinathan Nair]

Hi Michael,

I think your  interpretation is wrong. I think Non-ip here means it is layer 2 traffic. 

Non-IP and Layer 3 port channels both follow the configured load-balancing method, using the source, destination, or source and destination parameters. For example, when you configure load balancing to use the source IP address, all non-IP traffic uses the source MAC address to load balance the traffic while the Layer 3 traffic load balances the traffic using the source IP address. Similarly, when you configure the destination MAC address as the load-balancing method, all Layer 3 traffic uses the destination IP address while the non-IP traffic load balances using the destination MAC address.

http://www.cisco.com/c/en/us/td/docs/switches/datacenter/sw/4_2/nx-os/interfaces/configuration/guide/if_nxos/if_portchannel.html#wp1703858

This is my understanding. Hope this helps. 

Note : Please always rate all useful posts.

Thanks

Madhu.

[Michael Wingender]

The referenced document does not help. It is exactly the document which causes the wrong Interpretation(??). It is talking about L3 and non-IP (L2) Interfaces not about L3 traffic.

"The default load-balancing mode for Layer 3 interfaces is the source and destination IP address, and the default load-balancing mode for non-IP interfaces is the source and destination MAC address."

If Cisco means L3 traffic and non-ip traffic this document should say L3 traffic and non-IP traffic. Do you understand what I mean?

Br

Michael