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78
Chapter 3
IP Addressing
After picking the first available network number (172.16.0.4) given our
30-bit subnet mask and eliminating host IP addresses that are all ones and all
zeros, we have the following range of numbers: 172.16.0.5­172.16.0.6. The
broadcast address is all host bits on, or 172.16.0.7. We can take one of these
numbers and assign it to one side of the serial link. The other number can be
assigned to the other end of the serial link.
Next, we will calculate the range of IP addresses to use for our hub
segment, containing four router interfaces. We pick the first available net-
work address given our 29-bit subnet mask. In this case, the first available
network is 172.16.0.8, as shown in Table 3.10.
Last IP in
range
0 0 0 0 0 0 0 0
0 0 0 0 0 1 1 0
172.16.0.6
Broadcast
0 0 0 0 0 0 0 0
0 0 0 0 0 1 1 1
172.16.0.7
T A B L E 3 . 1 0
IP Address Range for Switched Segment in Figure 3.2
3rd Octet
4th Octet
Decimal IP Address
128 64 32 16 8 4 2 1
128 64 32 16 8 4 2 1
(Last 16 bits in bold)
Subnet Mask
1 1 1 1 1 1 1 1
1 1 1 1 1 0 0 0
255.255.255.248
Network
0 0 0 0 0 0 0 0
0 0 0 0 1 0 0 0
172.16.0.8
First IP in
range
0 0 0 0 0 0 0 0
0 0 0 0 1 0 0 1
172.16.0.9
Last IP in
range
0 0 0 0 0 0 0 0
0 0 0 0 1 1 1 0
172.16.0.14
Broadcast
0 0 0 0 0 0 0 0
0 0 0 0 1 1 1 1
172.16.0.15
T A B L E 3 . 9
Networks, Hosts, and Subnets for Figure 3.2 (continued)
3rd Octet
4th Octet
Decimal IP Address
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