Written Lab
99
following table shows the number of IP addresses required and the
subnet masks needed to support the network.
3.
Beginning with the segment requiring the greatest number of subnet
bits, begin allocating addresses.
We'll do the serial link first, since it has 30 bits of subnetting. Since all of
our addresses begin with 172.16, we will examine only the last 16 bits of the
IP address. In the following table, we show the subnet mask, in binary, and
the first and last IP number in the range. Remember that the host portion of
the address cannot be all ones or all zeros.
Description of
Segment
Number of IP
Addresses Required
Subnet Mask (Number
of Bits in Subnet)
Server farm
50 (Because the
maximum number of
servers is 50)
255.255.255.192 (26)
Ethernet user
segment
254 (Because a
Class C subnet was
specified)
255.255.255.0 (24)
Description of
Segment
Number of IP
Addresses Required
Subnet Mask (Number
of Bits in Subnet)
Serial link
2 (Because each of the
two routers needs one
IP address)
255.255.255.252 (30)
Computer lab
400 (Because each PC
needs its own IP
address)
255.255.254 (23)
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 1 0 0
255.255.255.252
Network
0 0 0 0 0 0 0 0
0 0 0 0 0 1 0 0
172.16.0.4
First IP in
range
0 0 0 0 0 0 0 0
0 0 0 0 0 1 0 1
172.16.0.5
Last IP in
range
0 0 0 0 0 0 0 0
0 0 0 0 0 1 1 0
172.16.0.6
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