21: your organization is using the 192.168.1.0/24 address space. you need 28 subnets. what subnet mask would you use to create these subnets?
　　a. 255.255.255.0

　　b. 255.255.255.128

　　c. 255.255.255.192

　　d. 255.255.255.224

　　e. 255.255.255.240

　　f. 255.255.255.248
　　
　　22: which of the following protocols maps ip addresses to mac addresses for connectivity to occur between two hosts?

　　a. arp

　　b. rarp

　　c. slarp

　　d. dhcp
　　
　　23: your junior network administrator cannot seem to ping a host in another network and asks you why it isn't working. which of the following is not an answer that you would give him?

　　a. the host's default gateway is down.

　　b. the destination host is not powered on.

　　c. the ip address of the router interface is incorrect.

　　d. the ip address of the switch to which the destination host connects is incorrect.

　　e. the host is in a different subnet.
　　
　　24: which of the following classes of ip addresses is utilized for multicasting?

　　a. class a

　　b. class b

　　c. class c

　　d. class d
　　
　　25: you give your it department a spreadsheet of ip addresses and their subnets. you receive a call from one of the junior techs asking what the /26 means next to the ip addresses. you tell her:

　　a. it represents the number of hosts possible on that subnetwork.

　　b. it represents the number of subnetworks that are being used.

　　c. it represents the class of ip address being used.

　　d. it represents the number of bits in the subnet mask that are 1.