LB persistence in source-ip template VS. method in service-group

toddmason

Hey All,

Can anyone tell me the difference between enabling persistence in a source-ip persist template applied to a virtual server vs. enabling the src-ip-only-hash method in a service-group? Both seem to say the same thing and if so which would take precedence? (if the other were configured otherwise)

slb template persist source-ip persist-service

slb virtual-server some-udp-service-vip x.x.x.x
port 999 udp
  service-group 999-group 
  template persist source-ip persist-service

slb service-group 999-group udp
  method src-ip-only-hash

If the goal is to make all client requests stick to the same back end server (perpetually even after session ages out, assuming it's available) which of the above would do this? Said another way, which of these are enabling the desired effect or take precedence?

The docs state template persistence selection of "the same server resources" whereas the service-group method type dictates "connecting session data flow to the back end server". Virtually the same language from my standpoint.

Thoughts anyone? Thank you.

mdunn

I believe both of these approaches will accomplish the goal. When a persist template is used, persistence information will appear in the session persist table, whereas with the load balancing method, you will only see session table information. The persistence table is synchronized to HA devices. However, assuming the same code revision and service-group configuration, both ACOS units should calculate the same hash for the load balancing method.

Using the persist template does allow you to leverage different load balancing methods. With src-ip-only-hash, a particular source IP will always use the same real server (if all service-group members are up), and this may not be desirable.

As for order of operations, if both were configured, I would expect the load balancing method to select the real server, and then the persist template would populate the session persist table with the information.

Hope that helps!