12. Roaming Flashcards
When a client roams in between 2 autonomous APs, what does the AP do with any leftover wireless frames after the client has left?
It forwards them to the new AP over the wired infrastructure because that’s where the clients’ MAC address now resides.
Roaming between two APs that are joined to the same controller is called what?
Intracontroller roaming.
10ms
What are the three techniques, Cisco controllers offer, to minimize the time and effort spent on key exchanges during roams?
- Cisco Centralized Key Management (CCKM)
- Key caching
- 802.11r
What does the client have to support to utilize CCKM during roaming?
Cisco Compatible Extensions (CCX)
How does CCKM work?
One controller maintains a database of clients and keys on behalf of its APs and provides them to other controllers and their APs as needed.
When roaming what is key caching?
Client maintains a list of keys used with prior AP associations and presents them as it roams.
How does 802.11r help a client when roaming?
The client can cache a portion of the authentication server’s key and presents that to future APs as it roams.
Roaming between two APs that are joined to different controller is called what?
Intercontroller roaming
What is a layer 2 intercontroller roam?
When a client roams between APs on different controllers but the WLANs are on the same VLAN
(20ms)
What’s another name for layer 2 intercontroller?
Local-to-local roam
How is a client able to maintain its IP address when roaming to an AP on a different controller and a different VLAN?
There is a CAPWAP tunnel maintained between the controllers.
In a layer 3 intercontroller roam, what is the controller called that maintains connectivity to the original VLAN?
Anchor controller
In a layer 3 intercontroller roam, what is the controller called that has the AP currently associated with the client?
Foreign controller
In order for controllers to execute a layer 2 or layer 3 roam between them, them must both be in what type group?
Mobility group
Why might a client have to do a full authentication when doing an intercontroller roam?
The controllers are not in the same mobility group.
What is the difference between a mobility domain and a mobility group?
It is a hierarchy. There are mobility groups within a mobility domain.
How many controllers can be in a mobility domain and how many in a mobility group?
72 in domain
24 in group
There are two distinct roles and functions involving mobility. What are the functions of a mobility controller (MC)?
Manages roaming
Performs RRM
Performs wireless IPS
Manages guest access
There are two distinct roles and functions involving mobility. What are the functions of a mobility agent (MA)?
Terminates CAPWAP tunnels
Maintains client database
Enforces security and QoS policies
In reference to mobility, there are two roaming coordination roles that exist from the client’s perspective. What are they?
Point of Presence (PoP) - IP address, security policies
Point of Attachment (PoA) - association, QoS
List the roaming hierarchy on converged controllers?
Mobility domain
Mobility group
Mobility subdomain
Switch peer group (SPG)
In converged controller roaming, whrere is the most efficient roaming happening?
When it’s with the same SPG
Each WCM functions as a MA but must be joined to an MC. Can a WCM function as an MC?
Yes
