How N+1 HA works over WAN?

[Ahmad El-Saka]

I have read that the N+1 HA model provides redundancy for geographically separated data centers.

As of my implementation for the the N+1 HA in one site, I understand that it works in Layer 2, as we connect the WLC as a trunk, connect APs as an access and add the VLAN ID to every interface we add and then assign these interfaces to SSIDs.

But over WAN we are in Layer 3, how does the backup controller work with VLANs that it don't know about?

Regards.

[Scott Fella]

When using N+1 and controllers separated by L3, you need to define the bland and interfaces for that location. When a controller fails, users will disassociate and then re-associate and obtain a dhcp from the new location. This is how N+1 works over L3.  So look at it like a total different site as traffic now will egress that location when there is a failover. 

-Scott 

*** Please rate helpful posts ***