VPC Load Balancing

[jamesconsterdine]

Hi All

We have two N7000's set up to provide a VPC to our wireless controller, but load balancing is uneven and I'm trying to work out if there's anything we can do, struggling to find the specific information in guides etc. 

The attached image shows the very basic connectivity. 1 x 1Gbps interface from each N7K set up as a VPC to the WLC. 

However almost all traffic is running down the link from N7K-1, with this interface hitting 90% utilization and alerting as a result. This makes sense I think, as the majority of the client/AP traffic comes from remote sites which are not yet dual connected, they are just connected to N7K-1. 

So the question is whether there's anything we can do to force some of the traffic to go via the link between the two N7Ks and then actively use the second link? 

If not, at what point would we expect that to happen? Only when the first link is at 100%?

Thanks for any advice

James

[Mark Malone]

This is just a suggestion you could try manipulate LB by changing it how it forwards traffic

I think src-dst mac is whats recommended but if its not working for you, you could try and change it see if it changes the flow and uses more of the second link

change it with port-channel load-balance xxx

7k1# sh port-channel load-balance
 System config:
  Non-IP: src-dst mac
  IP: src-dst l4port rotate 0
Port Channel Load-Balancing Configuration for all modules:
Module 3:
  Non-IP: src-dst mac
  IP: src-dst l4port rotate 0
Module 4:
  Non-IP: src-dst mac
  IP: src-dst l4port rotate 0
 

[Jon Marshall]

James

If you are talking about traffic going to the WLC from the Nexus switches then it will never use the vPC peer link and even if it did the packets would not be forwarded because of the vPC loop avoidance mechanism so it doesn't matter what load balancing algorithm you use.

If N7K1 has an active vPC port to the WLC and it sends the packet to N7K2 then N7K2 will drop it because it knows N7K1 has an active port and it should have been forwarded locally.

So even if the link becomes full utilised packets cannot be forwarded to the WLC via N7K2.

The obvious solution is to dual hone your connections to both Nexus switches.

Jon