thinQmaster Virtual testing partner Adaptive practice exams that find your weak spots and drill them. Every answer explained. From $69
Enroll

thinQmaster

Find your exam

Five questions free, before you decide.

Step 1 · choose a vendor

In one of our camps? Your practice exams come with the tuition — they are on your study page already.

Networking Fundamentals · Foundational

Class A Address

An IPv4 address with first octet 1-126 (leading bit 0) and a default mask of 255.0.0.0 (/8).

Definition

Class A networks have 8 network bits and 24 host bits, allowing 16,777,214 hosts each. The 10.0.0.0/8 block is reserved for private use, and 127.0.0.0/8, technically in the Class A range, is reserved for loopback. The 0.0.0.0/8 block is also reserved.

Example

10.50.3.7 is a private Class A address.

Exam tip

127.x.x.x is excluded from usable Class A ranges because it is loopback.

Related terms