Understanding Round Robin Load Balancing Behavior in SE and Tuning per-SE Distribution

Products

• VMware Avi Load Balancer

Issue/Introduction

1. Understanding Round Robin Load Balancing Behavior in SE and Tuning per-SE Distribution.
2. Unequal load distribution may be observed when an SE is deployed with more than one core.

Resolution

By default, when using the Round Robin (RR) load balancing algorithm in Avi Load Balancer, traffic distribution is done on a per-core basis within each Service Engine (SE). This can result in multiple cores from a single SE selecting the same backend server, which is expected behavior in the default configuration.

 

You may observe non-uniform distribution across backend servers when:

• A single SE with many cores is handling most of the traffic.

• You're expecting per-SE server selection (i.e., each SE should pick a unique server, regardless of how many cores it has

 

How to Enforce Per-SE Load Balancing in Round Robin

To modify the default behavior and ensure that each SE selects only one server, regardless of the number of cores, use the lb_algo_rr_per_se knob in the pool configuration.

 

Steps to Update Pool Setting

1. SSH into the Avi Controller and enter shell:

   ssh admin@<Controller_IP>

   shell

    

2. Enter configuration mode for the target pool:

    

   configure pool <POOL_NAME>

    

3. Enable per-SE RR algorithm:

   lb_algo_rr_per_se

   save

    

Refer: https://techdocs.broadcom.com/us/en/vmware-security-load-balancing/avi-load-balancer/avi-load-balancer/31-1/vmware-avi-load-balancer-configuration-guide/load-balancing-overview/load-balancing-algorithms.html