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New Member

Which way is better for AP redundant controllers configuration?

Hi,

I am wondering which of the two options is better in term of failover.

Option 1 – Specify primary, secondary, or tertiary controllers on each AP.

Option 2 - Specify primary backup and secondary backup controllers in Wireless->Access Points->Global Configuration.

If Option 1 is in use already, will failover time reduce if use option 2 as well with AP Fast Heartbeat Timer enable?

If option 1 is in use already but not option 2,  will there any be benefit to enabler AP Fast Heartbeat Timer and config shorter timeout values?

Thanks
Cedar

1 ACCEPTED SOLUTION

Accepted Solutions
VIP Purple

Which way is better for AP redundant controllers configuration?

Hi Cedar,

If you configure AP Fast Heartbeat, it will help APs to detect WLC failure more quick independant of any other settings.

If you have both option 1 & 2 configured, always option 1 will take precedance (so no point of configuring both), in case all primary, secondary, tertiary controllers failure it will use globack backup configured.

Below frome the 7.4 config guide pretty much explain this well. Pls go through it as well

http://www.cisco.com/en/US/docs/wireless/controller/7.4/configuration/guides/consolidated/b_cg74_CONSOLIDATED_chapter_01110011.html

  • You can configure primary and secondary backup controllers (which are used if primary, secondary, or tertiary controllers are not specified or are not responsive) for all access points connected to the controller as well as various timers, including heartbeat timers and discovery request timers. To reduce the controller failure detection time, you can configure the fast heartbeat interval (between the controller and the access point) with a smaller timeout value. When the fast heartbeat timer expires (at every heartbeat interval), the access point determines if any data packets have been received from the controller within the last interval. If no packets have been received, the access point sends a fast echo request to the controller.
  • The access point maintains a list of backup controllers and periodically sends primary discovery requests to each entry on the list. When the access point receives a new discovery response from a controller, the backup controller list is updated. Any controller that fails to respond to two consecutive primary discovery requests is removed from the list. If the access point’s local controller fails, it chooses an available controller from the backup controller list in this order: primary, secondary, tertiary, primary backup, and secondary backup. The access point waits for a discovery response from the first available controller in the backup list and joins the controller if it receives a response within the time configured for the primary discovery request timer. If the time limit is reached, the access point assumes that the controller cannot be joined and waits for a discovery response from the next available controller in the list.
  • When an access point's primary controller comes back online, the access point disassociates from the backup controller and reconnects to its primary controller. The access point falls back only to its primary controller and not to any available secondary controller for which it is configured. For example, if an access point is configured with primary, secondary, and tertiary controllers, it fails over to the tertiary controller when the primary and secondary controllers become unresponsive. If the secondary controller comes back online while the primary controller is down, the access point does not fall back to the secondary controller and stays connected to the tertiary controller. The access point waits until the primary controller comes back online to fall back from the tertiary controller to the primary controller. If the tertiary controller fails and the primary controller is still down, the access point then falls back to the available secondary controller.

Also this may be a useful post as well

http://mrncciew.com/2013/04/07/ap-failover/

HTH

Rasika

**** Pls rate all useful responses ****

4 REPLIES
Hall of Fame Super Gold

Which way is better for AP redundant controllers configuration?

Depends on your setup.

In our case we have two WiSM2 in an AP SSO configuration.  Both WiSM2 are located in two different chassis in two different location.  Because of this, I don't need to configure primary/secondary/tertiary controller.

If you have, for example, a WLC 2504 (which doesn't support AP SSO) I would individually specify the primary/secondary/tertiary controller on each AP.  I don't like to configure this on the Global Settings.

New Member

Re: Which way is better for AP redundant controllers configurati

I got your point. Thanks Leo.

Cedar

VIP Purple

Which way is better for AP redundant controllers configuration?

Hi Cedar,

If you configure AP Fast Heartbeat, it will help APs to detect WLC failure more quick independant of any other settings.

If you have both option 1 & 2 configured, always option 1 will take precedance (so no point of configuring both), in case all primary, secondary, tertiary controllers failure it will use globack backup configured.

Below frome the 7.4 config guide pretty much explain this well. Pls go through it as well

http://www.cisco.com/en/US/docs/wireless/controller/7.4/configuration/guides/consolidated/b_cg74_CONSOLIDATED_chapter_01110011.html

  • You can configure primary and secondary backup controllers (which are used if primary, secondary, or tertiary controllers are not specified or are not responsive) for all access points connected to the controller as well as various timers, including heartbeat timers and discovery request timers. To reduce the controller failure detection time, you can configure the fast heartbeat interval (between the controller and the access point) with a smaller timeout value. When the fast heartbeat timer expires (at every heartbeat interval), the access point determines if any data packets have been received from the controller within the last interval. If no packets have been received, the access point sends a fast echo request to the controller.
  • The access point maintains a list of backup controllers and periodically sends primary discovery requests to each entry on the list. When the access point receives a new discovery response from a controller, the backup controller list is updated. Any controller that fails to respond to two consecutive primary discovery requests is removed from the list. If the access point’s local controller fails, it chooses an available controller from the backup controller list in this order: primary, secondary, tertiary, primary backup, and secondary backup. The access point waits for a discovery response from the first available controller in the backup list and joins the controller if it receives a response within the time configured for the primary discovery request timer. If the time limit is reached, the access point assumes that the controller cannot be joined and waits for a discovery response from the next available controller in the list.
  • When an access point's primary controller comes back online, the access point disassociates from the backup controller and reconnects to its primary controller. The access point falls back only to its primary controller and not to any available secondary controller for which it is configured. For example, if an access point is configured with primary, secondary, and tertiary controllers, it fails over to the tertiary controller when the primary and secondary controllers become unresponsive. If the secondary controller comes back online while the primary controller is down, the access point does not fall back to the secondary controller and stays connected to the tertiary controller. The access point waits until the primary controller comes back online to fall back from the tertiary controller to the primary controller. If the tertiary controller fails and the primary controller is still down, the access point then falls back to the available secondary controller.

Also this may be a useful post as well

http://mrncciew.com/2013/04/07/ap-failover/

HTH

Rasika

**** Pls rate all useful responses ****

New Member

Re: Which way is better for AP redundant controllers configurati

Thanks Rasika the detail information.

The url you sent have both GUI snapshots and CLI commands. Love it.

Cedar

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