Figure 29 Ip Addressing: Class A - Nortel DMS-100 User Manual

152 Appendix E: Understanding IP and IP addressing

Figure 29 IP addressing: class A

Class A addresses range from 1.X.X.X to 127.X.X.X (standard network mask
is 255.0.0.0). Therefore, we can have 127-2 class A networks each with
16,777,216-2 hosts (if no subnets).
|
0
1 bit
| |
Class A indicator
For any class, the hostid can be split into a subnet id and a hostid depending
on customer requirements. This helps simplify routing to areas. For class A
network, the subnet id can range from 2 to 22 bits.
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 A networks have one of these special addresses; namely 10.0.0.0.
297-8991-910 Standard 03.01 August 1999
networkid
7
bits
|
2 to 22 bits
|
hostid
24 bits
Field subnet in table IPNETWRK
subnet id
|
Base_Tel-9
32
bits
|
|
hostid
2 to 22 bits
|