92
Chapter 3
IP Addressing
Therefore, by using IP unnumbered, the apparently discontiguous subnets,
shown in Figure 3.4, are actually supported. Understand that both sides of
the network must be the same address class. In other words, you can't bor-
row an IP address on one side from a 10.0.0.0 network and then from
172.16.0.0 on the other side of the point-to-point link.
There are a few things to be aware of before using IP unnumbered interfaces.
For example, IP unnumbered is not supported on X.25 or SMDS networks.
Also, since the serial interface has no IP number, you will not be able to ping
the interface to see if it is up, although you can determine the interface status
with SNMP. In addition, IP security options are not supported on an IP unnum-
bered interface.
Decimal-to-Binary Conversion Chart
F
or your convenience, Table 3.15 provides a decimal-to-binary chart
to help you with your IP addressing.
T A B L E 3 . 1 5
Decimal-to-Binary Chart
Decimal
Binary
Decimal
Binary
Decimal
Binary
Decimal
Binary
0
00000000
16
00010000
32
00100000
48
00110000
1
00000001
17
00010001
33
00100001
49
00110001
2
00000010
18
00010010
34
00100010
50
00110010
3
00000011
19
00010011
35
00100011
51
00110011
4
00000100
20
00010100
36
00100100
52
00110100
5
00000101
21
00010101
37
00100101
53
00110101
6
00000110
22
00010110
38
00100110
54
00110110
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