C. /21 INDICATES THAT THERE ARE 21 BITS USED FOR THE NETWORK ADDRE...

13. C. /21 indicates that there are 21 bits used for the network address of

an IP address and that there are 11 bits left over for host addresses,

corresponding to a decimal number of 2,048 (subtract 2 for addresses

with all 0s and all 1s, leaving 2,046). For more information on CIDR,

see Chapter 3.