BIGIP F5 LTM – Action on Service Down


“Action on Service Down” defines the action that should be taken once the pool member has been marked as “down” by the associated healthcheck, after it has been selected as the load balancing target for a connection.


To configure “Action on Service Down” goto the GUI and then to ‘Local Traffic / Pools’.



The 4 options are :

Reject : A reset is sent to both client and server.
Drop : Traffic on the established connection is silently dropped.
Reselect : A new pool member is selected and the existing connection is sent to the new pool member. This option is only useful when the pool member is a transparent device such as firewall or proxy server and/or a UDP virtual server.
None : Established connections will still be sent to the server whilst the client and server are responding. This is useful when session draining is required (i.e the server is marked down by the health-check but existing connections are still honored).

iRule Options

Should you wish to use the functionality of the “Action on Service Down” feature within an iRule then the following commands can be used.

LB_FAILED – Triggered when the pool member is unreachable or does not respond to a connection request.
LB::reselect – This command is used to selects the next available member in the current pool.

Rick Donato

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