多项选择题 During voice implementation，  which two required items are configured at an access layer switch connected to an IP phone to provide VoIP communication？（）

多项选择题 A network is deployed using best practices of the enterprise campus network model， including users with desktop computers connected via IP phones. Given that all components are QoS-capable，  where are the two optimal locations for trust boundaries to be configured by the network administrator？（）

单项选择题 Wireless has been operating correctly in the campus infrastructure. After the wireless controllers are upgraded from LWAPP to CAPWAP， access points no longer boot and operate normally.  What is the most likely issue causing this problem？（）