Talk:Cisco Application Control Engine (ACE) Troubleshooting Guide -- Troubleshooting Layer 4 Load Balancing

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Discussion about Troubleshooting Layer 4 Load Balancing

The document is very helpful, but one element is missing:

How do you troubleshoot dropped connections?

What can you do when the "dropped conns" counter increases?

Thanks for your questions. Here is some information about the dropped conns counter from the Cisco Technical Assistance Center (TAC):

Dropped Connections under a VIP

The dropped conns counter under a VIP in the output of the show service policy detail command is incremented whenever a connection request destined to that VIP is rejected by the ACE. There are several reasons why the ACE rejects such connection requests. For example:

  • If all the real servers in the server farm associated with the VIP go down, then the VIP will go down. So, all the incoming connections to that VIP are rejected.
  • If the URL in a connection request to the VIP is unknown, then the connection request is rejected.
  • If the server that the ACE selects to load-balance the connection doesn't respond to the request, then, after maximum retries, the ACE rejects the connection.

The dropped conns counter is cumulative and the value may comprise entries from any of the following show command counters:

  • show stats loadbalance
Total Layer4 rejections
Total Layer7 rejections
Total Layer4 LB policy misses
Total Layer7 LB policy misses
Total times rserver was unavailable
  • show stats connection
Total Connections Timed-out
Total Connections Failed
  • The failures counter of the show serverfarm serverfarm_name command.
  • The Total drop decisions counter of the show stats inspect command.
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