WLC 5520 SSO Failover behavior

[WVD]

Hello everyone,

I can’t find a definitive answer regarding the behavior of SSO and I'm looking for some help here. What happens to the Primary controller when a failover happens and it returns? Is it put into Standby-Hot mode until manual intervention or does it return to Active?

I've come across an old post that says:

There´s no preempt for Cisco WLC HA process.

Cisco Says:

"There is no preempt functionality. When the previous Active WLC comes back, it will not take the role of the Active WLC, but will negotiate its state with the current Active WLC and transition to a Standby state. The Active and Standby decision is not an automated election process. The Active/Standby WLC is decided based on HA SKU (Manufacturing Ordered UDI) from release 7.3 onwards. A WLC with HA SKU UDI will always be the Standby WLC for the first time when it boots and pairs up with a WLC running a permanent count license. For existing WLCs having a permanent count license, the Active/Standby decision can be made based on manual configuration."

I'm not sure if this still applies to 8.5 onwards.

Would appreciate some input on this.

Thank you.

[richard.priest · Accepted solution]

I'm pretty sure that the behaviour is exactly the same in 8.5. It certainly behaves in this way on 8.3. i.e. when the 'primary' device comes back online it then becomes the secondary controller unless there is manual intervention.

[omz]

Hi 

No preemption. 

[Haydn Andrews]

When the Primary WLC comes back online it re-joins the SSO as the secondary WLC until the secondary fails or a manual fail over is initiated. Unlike HSRP there is no pre-empt to make it fail back as primary

[RaffyLindogan]

Hi mate,

It is designed for SSO deployment that there is no pre-emption so you can control the maintenance window.

The previous primary WLC will take the standby role until the current primary will fail.

Cheers,

Raffy