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Community Member

TCP state when a VIP goes into OUT OF SERVICE

Hi,

Can somebody tell me the TCP behaviour in this scenario.

- An end user is browsing a website via HTTP through an ACE

- Both web servers start to fail the HTTP probe because the downstream SQL server fails

- The VIP policy goes into a OUT OF SERVICE status

Does the ACE send a TCP reset to the end user at this point because the VIP is OUT OF SERVICE?

Cheers

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Accepted Solutions
Cisco Employee

Hi,By default ACE will do

Hi,

By default ACE will do nothing if a real server fails. But you can configure it to send the RST. Below is from user guide:

 Configuring the ACE Action when a Server Fails

You can set the action that the ACE takes with respect to connections if any real server fails in a server farm. You can configure the failure action by using the failaction command in either server farm host or server farm redirect configuration mode.

The syntax of this command is as follows:

failaction {purge | reassign}

The keywords and options are as follows:

•purge—Instructs the ACE to remove all connections to a real server if that real server in the server farm fails after you enter this command. The appliance sends a reset (RST) to both the client and the server that failed.

•reassign—Instructs the ACE to reassign the existing server connections to the backup real server (if configured) on the same VLAN interface if the real server fails after you enter this command. If a backup real server has not been configured for the failing server, this keyword has no effect and leaves the existing connections untouched in the failing real server.

More details can be found at :

http://www.cisco.com/c/en/us/td/docs/app_ntwk_services/data_center_app_services/ace_appliances/vA3_1_0/configuration/slb/guide/slbgd/rsfarms.html#wp1117375

Regards,

Kanwal

Note: Please mark answers if they are helpful.

2 REPLIES
Cisco Employee

Hi,By default ACE will do

Hi,

By default ACE will do nothing if a real server fails. But you can configure it to send the RST. Below is from user guide:

 Configuring the ACE Action when a Server Fails

You can set the action that the ACE takes with respect to connections if any real server fails in a server farm. You can configure the failure action by using the failaction command in either server farm host or server farm redirect configuration mode.

The syntax of this command is as follows:

failaction {purge | reassign}

The keywords and options are as follows:

•purge—Instructs the ACE to remove all connections to a real server if that real server in the server farm fails after you enter this command. The appliance sends a reset (RST) to both the client and the server that failed.

•reassign—Instructs the ACE to reassign the existing server connections to the backup real server (if configured) on the same VLAN interface if the real server fails after you enter this command. If a backup real server has not been configured for the failing server, this keyword has no effect and leaves the existing connections untouched in the failing real server.

More details can be found at :

http://www.cisco.com/c/en/us/td/docs/app_ntwk_services/data_center_app_services/ace_appliances/vA3_1_0/configuration/slb/guide/slbgd/rsfarms.html#wp1117375

Regards,

Kanwal

Note: Please mark answers if they are helpful.

Community Member

Thank you for the response.

Thank you for the response. We have failaction purge configured already - we ran wireshark and actually saw a TCP RST when the VIP went out of service so that's all good!

Cheers

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