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ACE module not load balancing across two servers

tstrom
Level 1
Level 1

We are seeing an issue in a context on one of our load balancers where an application doesn't appear to be load balancing correctly across the two real servers.  At various times the application team is seeing active connections on only one real server.  They see no connection attempts on the other server.  The ACE sees both servers as up and active within the serverfarm.  However, a show serverfarm confirms that the load balancer sees current connections only going to one of the servers.  The issue is fixed by restarting the application on the server that is not receiving any connections.  However, it reappears again.  And which server experiences the issue moves back and forth between the two real servers, so it is not limited to just one of the servers.

The application vendor wants to know why the load balancer is periodically not sending traffic to one of the servers.  I'm kind of curious myself.  Does anyone have some tips on where we can look next to isolate the cause?

We're running A2(3.3).  The ACE module was upgraded to that version of code on a Friday, and this issue started the following Monday.  The ACE has 28 contexts configured, and this one context is the only one reporting any issues since the upgrade.

Here are the show serverfarm statistics as of today:

ACE# show serverfarm farma-8000
serverfarm     : farma-8000, type: HOST
total rservers : 2
---------------------------------
                                                ----------connections-----------
       real                  weight state        current    total      failures
   ---+---------------------+------+------------+----------+----------+---------
   rserver: server#1
       x.x.x.20:8000      8      OPERATIONAL  0          186617     3839
   rserver: server#2
       x.x.x.21:8000      8      OPERATIONAL  67         83513      1754

2 Replies 2

yushimaz
Cisco Employee
Cisco Employee

Are you enabling sticky feature? What kind of predictor are you using?

If sticky feature is enabled and one rserver goes down, traffic will leans to one side.

Even after the rserver retuns to up, traffic may continue to lean due to sticky feature.

The behavior seems to depend on the configuration.

So, please let me know a part of configuration?

Regards,

Yuji

rathinilesh
Level 1
Level 1

Hi could you please post your config related to this VIP ?

Regards,

Nilesh