i had to buy two 3850 in order to have HA in one floor?
You stack them both together to form a single logical unit. However, for example your APs are in Switch 1 and Switch 1 fails, then someone needs to manually move the APs directly connected to Switch 1 to be directly connected to Switch 2.
Q. What type of high availability is available with the Cisco 5760 WLC? A. The Cisco 5760 WLC in centralized deployment mode (also known as local mode) supports N+1 resiliency. It also supports multiple link aggregation (LAG) to protect against link failures while maintaining throughput.
Q. What high availability is available with the Cisco Catalyst 3850?
A. The Cisco Catalyst 3850 supports subsecond failover through stacking. For wireless, access point Stateful Switch Over (SSO) is supported.
Page 58-71 in the below presentation talks about HA on this CA platforms. Please go through it.
Transferring Crash file from standby: Login to the Active WLC in HA.
From CLI: (Cisco Controller) >transfer upload datatype crash (Cisco
Controller) >transfer upload filename (Cisco
Controller) >transfer upload mode tftp (Cisco Controller) >transfer
This is the start of a display filter cross reference between Wireshark
and OmniPeek. The 1st installment is a table of advanced filters. More
filters will be added as time allows. It is a living doc, so check back
for changes every so often Please feel f...