Questions on ACE operation

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Sep 24th, 2008
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We are deploying a Data Center with Cat 6500, FWSM and ACE (in bridged mode, for layer 4 load-balancing between http servers), and we are experiencing intermittent performance issues (the system is not yet under production).

During our investigation, we captured traffic before and after the ACE and noticed the following things :

¤ Half of sessions are initiated from the standby ACE to the real servers whereas FT config and status seem ok. Is this normal ?

¤ An analysis software reports excellent response times (0.15 ms) but too fast TCP retransmissions (between the ACE and the real servers); displaying the connection dynamics, we see that each TCP packet (SYN, ACK, etc.) is sent at least 3 times consecutively. Is this normal behavior ?

Besides, we configured TCP probes with a 20s interval. When a Web server comes up, it takes the ACE too much more than 20s to consider it up. Is this normal ?

Note : http probes showed to be somewhat unstable.

Thank you for your help.

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sachinga.hcl Wed, 09/24/2008 - 05:29
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the default or sdtandard is is 60 sec , if you like you can select the fast one which is having 4 sec interval.

sboukef Wed, 09/24/2008 - 23:12
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He have just upgraded due to the instability of the SMTP probes. Here is an extract from sh version :


loader: Version 12.2[120]

system: Version A2(1.1) [build 3.0(0)A2(1.1) adbuild_00:25:02-2008/06/05_/a


system image file: [LCP] disk0:c6ace-t1k9-mz.A2_1_1.bin

Gilles Dufour Thu, 09/25/2008 - 02:50
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1/ depending on how you captured the trace (ie vlan capture) you may see the same packet multiple time in trace which confuses traffic analyser.

2/ the standby will have probes to the real server as well. So, it is normal to see probes from the standby

3/ the default pass count is 3.

So it takes 3 successful probe before considering a server as alive.



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