Hey Charlie,
I came across this thread while looking up other information about the same timer settings you asked about. I know it's been a minute since you posted but I'll add what I've learned in case any others come across this.
Fast Heartbeat Timeout – 0 s
Purpose: This is used for rapid detection of a failure in certain high-availability (HA) scenarios.
Value: 0 seconds means disabled by default.
When used: If enabled, the WLC sends very frequent heartbeat messages to its peer (in an HA pair) to detect failure almost instantly. Useful for sub-second failover but consumes more CPU and bandwidth.
Heartbeat Timeout – 30 s
Purpose: This is the standard heartbeat mechanism between WLC and its HA peer.
Value: 30 seconds means the WLC waits up to 30 seconds without receiving a heartbeat before declaring the peer as down.
Impact: If the peer fails, the standby controller will take over after this timeout expires.
Retransmit timers apply to CAPWAP control messages between WLC and APs.
Count – 5
The WLC will retry sending a CAPWAP control message up to 5 times if no acknowledgment is received.
Interval – 3 s
The WLC waits 3 seconds between each retransmission attempt.
So if an AP doesn’t respond, the WLC will try 5 times at 3-second intervals (total ~15 seconds) before considering the AP unreachable for that message.
