servers behind ACE periodically become unreachable

DanilZhig · ‎08-11-2009

I've got an implementation with one ACE module and two DNS servers behind it. Balancing is even but the "show serverfarm detail" command shows a very high failures level (about 1/4 of the total connections).

Moreover - both servers become unreachable from outside from time to time. I graph server performance with MRTG and get gaps in my graph during the time when the servers are unreachable, but "show serverfarm detail" shows non-zero current connection counters.

How could this behaviour be explained?

Gilles Dufour · ‎08-13-2009

you need a sniffer trace to see exactly what is happening.

If ACE counts failures, it means it didn't see the response from the server.

So, get a sniffer trace in front and back of ACE (tengig interface preferably) and wait for the problem.

Then stop the trace and check if for every request you have a response.

G.