多项选择题 EIGRP is being used as the routing protocol on the PassGuide network. Whiletroubleshooting some network connectivity issues，you notice a large number of EIGRP SIA（StuckinActive）messages. What causes these SIA routes（）

单项选择题 At which lay er of the OSI model does the Spanning Tree Protocol (STP) operate at（）

多项选择题 Which two statements about the Cisco Aironet Desktop Utility (ADU) are true（）