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ACE hot-standby

Answered Question
Mar 20th, 2014
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Hi,

I have two ACE20 module installed in two Catalyst 6505 chassis, they are configured in fail-over mode with 3 virtual contexts, one admin conterxt and two user contexts. One ACE is Active for Admin context and host-standby for the other two contexts, and viceversa the second ACE is Active for user contexts and hot-standby for Admin context .  When I look for incoming connection to balanced services in user contexts, I see connections on both ACE, i mean either on Active and Stand-by but I expected to see just Active ACE managing incoming connections while no connections at all on Stand-by.

Is it correct? Is it a strange behaviour due any wrong configuration?

Pleas could anyone help me?

Thanks in advance

Angelo

Correct Answer by Fnu Kanwaljeet Singh about 3 years 5 months ago

Hi Angelo,

The actual connection itself only gets handled by ACTIVE device, only connection entry in connection table gets replicated/copied so that in case ACTIVE goes down, STANDBY knows about the connection and when packet will come to it , it will simply refer the connection table and forward it to the server and if no entry is found, take a loadbalance decision. That's why you don't see existing connections going down when stanbdy ACE becomes ACTIVE due to "ACTIVE" being down.

Show resource usage all in Admin context or show resource usage in particular context commands are sufficient to see the resource usage on the device.

Regards,

Kanwal

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Fnu Kanwaljeet Singh Thu, 03/20/2014 - 05:20
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  • Cisco Employee,

Hi Angelo,

This type of set up is perfectly normal. By default, ACE replicates the connection table from ACTIVE ACE or contexts to STANDBY ACE or contexts. So if you are implying on the basis of "show connection" output that connection is handled by both ACE's then don't worry about it. This is default behavior of ACE so that in an event of failover, standby ACE knows where to pick up. This is essential for seamless failover.

Let me know if you have any questions.

Regards,

Kanwal

 

ANGELO DE MASI Thu, 03/20/2014 - 05:36
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Hi Kanwal, thanks for your reply.

Does it mean that I should have to see the same connection first arriving on Active ACE and then replicated on the Hot-standby one?

So cause I have to measure the resource usage actually in use by contexts for future needs, is it sufficient to look for show resource usage or show resource all output on Active ACE?

thanks

angelo

Correct Answer
Fnu Kanwaljeet Singh Thu, 03/20/2014 - 05:50
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  • Cisco Employee,

Hi Angelo,

The actual connection itself only gets handled by ACTIVE device, only connection entry in connection table gets replicated/copied so that in case ACTIVE goes down, STANDBY knows about the connection and when packet will come to it , it will simply refer the connection table and forward it to the server and if no entry is found, take a loadbalance decision. That's why you don't see existing connections going down when stanbdy ACE becomes ACTIVE due to "ACTIVE" being down.

Show resource usage all in Admin context or show resource usage in particular context commands are sufficient to see the resource usage on the device.

Regards,

Kanwal

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