A network administrator is planning a network installation for a large organization. Ther design requires 100 separate subnetworks, so the company has acquired a Class B network address. What subnet mask will provide the 100 subnetworks required, if 500 usable host addresses are required per subnet?

　　A. 255.255.240.0

　　B. 255.255.248.0

　　C. 255.255.252.0

　　D. 255.255.254.0

　　E. 255.255.255.0

　　F. 255.255.255.192

　　Answer: D

　　A network is very congested. Currently all the devices are connected through a hub. Which solution would best decrease congestion on the network?

　　A. Add a second hub.

　　B. Replace the hub with a router.

　　C. Replace the hub with a switch.

　　D. Replace the hub with a repeater.

　　Answer: B。分析：router可以隔离广播。用switch其实也可以，必须注明使用VLAN，但题里没说。