112
Chapter 3
IP Addressing
14.
B. The command to set a default route in Cisco IOS is set ip route
0.0.0.0 0.0.0.0 next_hop
(where next_hop can be a local inter-
face or the IP of an adjacent router interface).
15.
C. On a serial link, we need only two IP addresses, one for each side
of the link. A subnet mask of 255.255.255.252 has only two host bits,
which gives us a maximum of two host IP addresses (2
2
2 = 2), which
is exactly what we need for our serial link.
16.
A, C. Although an IP number can be represented in practically any
base of numbering system, dotted-decimal and binary are the most
common representations.
17.
A, B, C. An IP address is 32 bits in length. An octet is eight bits in
length. Therefore, four octets equal 32 bits. Since a byte is eight bits,
four bytes also equal 32 bits.
18.
A, C, D. Route summarization is not compatible with IGRP, because
IGRP is a classful routing protocol, meaning that it does not carry sub-
net information in its routing updates.
19.
D. With 25 bits of subnetting, we have the last seven bits to use as the
host address. If we set each of these last seven bits to 1 (the definition
of a broadcast address), then we get 172.16.1.127.
20.
C. If you convert 224 to binary, you get 11100000. With five host bits
(i.e., bits set to 0 in the subnet mask), you can support 30 host
addresses (2
5
2 = 30, where 5 is the number of host bits).
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