11. Controller Discovery Flashcards
What are the most common AP states in their sequence order?
- AP boots
- WLC discovery
- CAPWAP tunnel
- WLC join
- Download image
- Download config
- Run
- Reset
During the CAPWAP tunnel state the AP and WLC authenticate each other using what method?
The exchange digital certificates.
Under what circumstances might an AP need to download a new code image?
AP joins a WLC but doesn’t have the same version of code.
A code upgrade is performed on the WLC and all assocate AP will need to download the new code.
WLC fails, causing the AP to join another WLC which doesn’t have the same code.
The goal of the WLC discovery state is to build a list of live candidate controller using what methods?
Prior knowledge of WLCs
DHCP and DNS info
Broadcast on the local subnet
To discover a WLC, an AP send what kind of frame over what port?
CAPWAP Discovery Request over UDP port 5246
WLC send back a CAPWAP Discovery Response
What is the sequence of WLC discovery process?
- Broadcast on local subnet
- Use locally stored WLC addresses
- Use DHCP
- Use DNS
- If none of the steps have worked the AP resets and starts the process all over.
An AP can be “primed” with how many controllers which are stored in non-volatile memory?
Three - primary, secondary, and tertiary.
An AP should a save up to how many controllers that have been previously joined?
Eight
Which DHCP option can suggest a list of WLC addresses?
Option 43
When discovering WLCs, an AP will try to resolve what name using DNS?
CISCO-CAPWAP-CONTROLLER.localdomain
What are the steps in the WLC selection process (deciding which controller to join)?
- Try primed addressed in succession
- Try the master controller (discovered thru broadcast)
- Try the least-loaded controller (during discovery phase controllers report their load)
What is the purpose of APs having a priority value?
If a controller reaches its capacity and an additional AP try to join, the controller tries to accommodate as man higher priority APs as possible.
What are the available settings for an APs priority value?
Low
Medium
High
Critical
Will an AP that has failovered to the secondary controller, move back to the primary controller once it’s available?
Normally no. You would have to globally enable the AP Fallback feature.
What is the default keep alive time being sent by the AP?
30 seconds
