IP Addressing

1 Networking Overview

Valid subnet masks The valid subnets for each Class of address are:

Class A

Class B:

Class C

(default 255.0.0.0)

(default 255.255.0.0)

(default 255.255.255.0)

 

 

 

255.192.0.0

255.255.192.0

255.255.255.192

 

 

 

255.224.0.0

255.255.224.0

255.255.255.224

 

 

 

255.240.0.0

255.255.240.0

255.255.255.240

 

 

 

255.248.0.0

255.255.248.0

255.255.255.248

 

 

 

255.252.0.0

255.255.252.0

255.255.255.252

 

 

 

255.254.0.0

255.255.254.0

 

 

 

 

255.255.0.0

255.255.255.0

 

 

 

 

255.255.128.0

255.255.255.128

 

 

 

 

255.255.192.0

255.255.255.192

 

 

 

 

255.255.224.0

255.255.255.224

 

 

 

 

255.255.240.0

255.255.255.240

 

 

 

 

255.255.248.0

255.255.255.248

 

 

 

 

255.255.252.0

255.255.255.252

 

 

 

 

255.255.254.0

 

 

 

 

 

255.255.255.0

 

 

 

 

 

255.255.255.128

 

 

 

 

 

255.255.255.192

 

 

 

 

 

255.255.255.224

 

 

 

 

 

255.255.255.240

 

 

 

 

 

255.255.255.248

 

 

 

 

 

255.255.255.252

 

 

 

 

 

Notice that all 5 valid Class C subnet masks can also be valid Class B or Class A subnet masks, and all 13 valid Class B subnet masks can also be valid Class A subnet masks.

For example, 255.255.255.224 is a valid subnet mask for all three address classes. It allows 6 (232) subnetworks for Class C addresses, 2046 (2112) subnetworks for Class B addresses and 524,286 (2192)subnetworks for Class A addresses. Each of these subnetworks can have 30 (252) hosts.

Administration for Network Connectivity

 

 

555-233-504 — Issue 1 — April 2000

CID: 77730

21

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Image 41
Lucent Technologies Release 8.2 manual Class a Class B Class C Default