Can LTM be used to configure Active and Passive Servers?

Hi Manc,

Yes it's definitely doable with LTM. You can do this either 2 ways : iRule or point-n-click configuration.

Point-n-click method

Basically you setup a single pool that is configured for Priority Load balancing

For Example:

You have 4 servers and you want 2 of the servers active all the time, but as soon as 2 of them fail due to the health check, then the other 2 servers come on line. If the 2 primary servers come back then return the traffic.

The structure would be

Pool A

Server 1 Priority 100 ratio 1

Server 2 Priority 100 ratio 1

Server 3 Priority 50 ratio 1

Server 4 Priority 50 ratio 1

You would probably add persistence so that you don't abruptly move connections during a failback and rather wait for the existing connection to close. However, this all depends entirely on the application requirements for persistence.

There are more details on how to do this on the F5 Configuration Guide you can find on http://ask.f5.com

iRule Method

The reason why you would want to use iRules is that is basically allows you even more granular control over how you want configure your active/passive configuration.

Here is a simple example

when CLIENT_ACCEPTED {
  if { [active_members active_pool ] >= 1 } {
   pool active_pool
  } else {
  pool passive_pool
 }
}

This iRule assumes you have defined 2 different pools.

I hope this helps

Bhattman