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154 Appendix E: Understanding IP and IP addressing
297-8991-910 Standard 03.01 August 1999
Figure 31 IP addressing: class B
| |
14
32
networkid hostid
bits
|
hostid
bits
2 bit
2 to 14 bits
Class B indicator
| ||
subnet id
||
|
2 to 14 bits
10
therefore, we can have 16384-2 class B networks each with 65536-2 hosts (if no subnets).
Class B addresses range from 128.0.X.X to 191.255.X.X (standard network mask is 255.255.0.0),
Note 1:
Network ids and host ids which are comprised of all 1’s or all 0’s are reserved,
therefore, subtract 2 from the subnet id and hostid to get the actual count.
Note 2:
There are also special addresses that are reserved for ‘unconnected’ networks
(networks that use IP but are not connected to the Internet). Class B networks
have 16 of these special addresses ranging from 172.16.0.0 to 172.31.0.0.
Base_Tel-11
For any class, the hostid can be split into a subnet id and a hostid depending on custom-
er requirements. This helps simplify routing to areas. For class B network, the subnet id
can range from 2 to 14 bits.
16 bits
Field subnet in table IPNETWRK