Exam 350-401 topic 1 question 143 discussion

B is the correct answer. If all the controllers within a mobility group are not using the same virtual interface, inter-controller roaming may appear to work, but the handoff does not complete, and the client loses connectivity for a period of time.

"All controllers must be configured with the same mobility group name. All controllers must be configured with the same virtual interface IP address. If necessary, you can change the virtual interface IP address by editing the virtual interface name on the Controller > Interfaces page. If all the controllers within a mobility group are not using the same virtual interface, inter-controller roaming may appear to work, but the handoff does not complete, and the client loses connectivity for a period of time."

B is the correct

answer A is also correct so why B?

The virtual interface IP address is a logical interface on the wireless controller that is used for mobility management, DHCP relay, and web authentication2. The virtual interface IP address must be configured on each controller in the network, and it must be the same on all controllers that are part of the same mobility group2. When a wireless client roams between two different controllers, the client’s IP address and subnet remain unchanged, and the client’s data traffic is tunneled from the foreign controller (the controller to which the client roams) to the anchor controller (the controller from which the client roams) using the virtual interface IP address as the tunnel endpoint2. If not all of the controllers within the mobility group are using the same virtual interface IP address, the mobility tunnel between them may not be established or maintained correctly, and the client may experience a network connectivity outage during roaming2. To avoid this problem, we need to ensure that all of the controllers within the mobility group are using the same virtual interface IP address, and that this IP address is routable and reachable across the network2.

https://www.cisco.com/c/en/us/td/docs/wireless/controller/7-4/configuration/guides/consolidated/b_cg74_CONSOLIDATED/m_configuring_virtual_interfaces.pdf

how can wlcs with different mobility group names can belong to the same mobility group?

A looks to be a legitimate answer. Since not all controllers in the mobility group using the same mobility group name, network outage may happen if client roams out to a controller with different mobility group

B is the correct answer

B is the correct answer, admin ?

B Response / A prerequisite for configuring Mobility Groups is "All controllers must be configured with the same virtual interface IP address". If all the controllers within a mobility group are not using the same virtual interface, inter-controller roaming may appear to work, but the handoff does not complete, and the client loses connectivity for a period of time. -> Answer B is correct. Reference: https://www.cisco.com/c/en/us/td/docs/wireless/controller/8-5/configguide/b_cg85/ mobility_groups.html

according cisco link, there is no virtual ip concept, triky question

The correct answer is: B. Not all of the controllers within the mobility group are using the same virtual interface IP address.

http://what-when-how.com/deploying-and-troubleshooting-cisco-wireless-lan-controllers/configuring-mobility-groups-cisco-wireless-lan-controllers/ Same virtual interface IP address: If the virtual IPs are not the same between the controllers, the handoff of the client database entry will not take place and the client will be disconnected for a short period. ------- I think B is correct

Provided answer is correct

- different (Name) Mobility Groups ==> the client need to reauthenticate (unless the new controller in the new Mobility Group is in the Mobility List of the Last Controler, in this case the roamin will be seamless) - Different Virtual Ip adresses for the controllers on the same Mobility Group, the Client will experience a network outage. so i think the more adequate answer is B.

Can the APs Join a WLC That Belongs to a Mobility Group That is Different From the Currently Associated Mobility Group? Yes. By default , when a WLC goes down, the APs registered to this WLC failovers to another WLC of the same Mobility Group, if the LAP is configured for failover. However, if a backup Controller Support is configured, then it can be any WLC even outside the Mobility Group and the access points failovers to controllers even outside the Mobility Group. Refer toN+1 High Availability Deployment Guide for more information.