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Stan_Ward_01_13's avatar
Stan_Ward_01_13
Icon for Nimbostratus rankNimbostratus
Oct 09, 2015

Why LB_FAILED when pool members are up?

I have an SSL VIP with two SSL pool members, both of which are up. The iRule LB_FAILED event is triggering. A tcpdump shows the health checks to the pool members (working and shown as green in the ...
Kevin_Stewart's avatar
Kevin_Stewart
Icon for Employee rankEmployee
Oct 09, 2015

Based on the description of the event:

 

LB_FAILED is triggered when LTM is ready to send the request to a pool member and one hasn’t been chosen (the system failed to select a pool or a pool member), is unreachable (when no route to the target exists), has reached a queue limit, or is non-responsive (fails to respond to a connection request).

 

https://devcentral.f5.com/wiki/iRules.LB_FAILED.ashx

 

which implies in most cases a TCP connection (layer 4) or routing (layer 3) issue. If you don't even see a TCP SYN from the BIG-IP, then I'd be looking at route or queue limits.