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Chapter 3
IP Addressing
We can use our formula 2n 2 = number of hosts to create a handy reference
chart to quickly determine how many hosts can be supported for any given
subnet mask, as shown in Table 3.7. The table goes up to only 1022 hosts,
because Cisco has a design recommendation that you should not have a non-
routed network segment with more than 500 hosts (due to performance prob-
lems caused by broadcast traffic). To confuse you further, understand that
some Cisco documentation states that the number of hosts on a segment can
be up to 800! Just keep in mind the amount of traffic when making this
decision.
T A B L E 3 . 7
Number of Hosts Needed in Figure 3.2
Maximum Number of Hosts
Bits in Subnet Mask
Subnet Mask
2
30
255.255.255.252
6
29
255.255.255.248
14
28
255.255.255.240
30
27
255.255.255.224
62
26
255.255.255.192
126
25
255.255.255.128
254
24
255.255.255.0
510
23
255.255.254.0
1022
22
255.255.252.0
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