AppendixC. Lists of Reserved Ports, ICMP Types and Codes, and Internet Protocols
1-set bits Mask IP address class
13 255.248.0.0 5
14 255.252.0.0 6
15 255.254.0.0 7
16 255.255.0.0 0
17 255.255.128.0 1
18 255.255.192.0 2
19 255.255.224.0 3
20 255.255.240.0 4
21 255.255.248.0 5
22 255.255.252.0 6
23 255.255.254.0 7
24 255.255.255.0 0
25 255.255.255.128 1
26 255.255.255.192 2
27 255.255.255.224 3
28 255.255.255.240 4
29 255.255.255.248 5
30 255.255.255.252 6
31 255.255.255.254 7
32 255.255.255.255 8
Example:We want to split the network 130.234.250.0/25 (i.e., 130.234.250.0-130.234.250.127) into four subnets.
Thenetmask for each subnet will be 27 bits, which means 255.255.255.224. This netmask is in IP class 3. The
secondtable gives us the following available intervals: 0-31, 32-63, 64-95, and 96-127 (then we are out of IP
addresses).One of the subnets will be 130.234.250.64/27 (130.234.250.64-130.234.250.95).
Class IP
intervals
0 0-255
1 0-127 128-255
2 0-63 64-127 128-191 192-255
3 0-31 32-63 64-95 96-127 128-159 160-191 192-223 224-255
4 0-15 16-31 32-47 48-63 64-79 80-95 96-111 112-127
128-143 144-159 160-175 176-191 192-207 208-223 224-239 240-255
5 0-7 8-15 16-23 24-31 32-39 40-47 48-55 56-63
64-71 72-79 80-87 88-95 96-103 104-111 112-119 120-127
128-135 136-143 144-151 152-159 160-167 168-175 176-183 184-191
192-199 200-207 208-215 216-223 224-231 232-239 240-247 248-255
6 0-3 4-7 8-11 12-15 16-19 20-23 24-27 28-31
32-35 36-39 40-43 44-47 48-51 52-55 56-59 60-63
64-67 68-71 72-75 76-79 80-83 84-87 88-91 92-95
96-99 100-103 104-107 108-111 112-115 116-119 120-123 124-127
128-131 132-135 136-139 140-143 144-147 148-151 152-155 156-159
160-163 164-167 168-171 172-175 176-179 180-183 184-187 188-191
192-195 196-199 200-203 204-207 208-211 212-215 216-219 220-223
224-227 228-231 232-235 236-239 240-243 244-247 248-251 252-255
138