IPv4, masks and CIDR
The 32-bit address, the mask and the /n notation, network part and host part, network address, broadcast address, range and number of hosts, and classes A, B, C as a historical landmark.
- 30 cards
- 6 topics
- Free
The outline, topic by topic
Each topic is weighted the way the exam weighs it.
- Concepts
- Questions
- Sort and link
- The numbers
- Scenarios
- Understand
A few cards from the deck
IPv4 address: what is it?
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A 32-bit number that identifies an interface on a network, written as four decimal bytes separated by dots.
192.168.1.10is11000000.10101000.00000001.00001010. Each byte goes from 0 to 255, hence 2^32 addresses in all, a little over 4 billion.Which dotted mask matches /20?
255.255.240.0255.255.248.0255.255.224.0255.240.0.0
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255.255.240.020 = 8 + 8 + 4: two full bytes and 4 bits set in the third, i.e.
11110000= 240.248would be a /21 and224a /19.A /26 mask leaves … bits to the host part, i.e. … hosts at most.
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A /26 mask leaves 6 bits to the host part, i.e. 62 hosts at most.
32 - 26 = 6 host bits, hence 2^6 = 64 addresses. Take away the network and broadcast addresses: 62 machines at most.
Subnet mask: what is it?
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A 32-bit value made of consecutive 1s then 0s, which says which bits of an address identify the network and which identify the machine.
255.255.255.0is 24 ones followed by 8 zeros. The bits set to 1 form the network part, the bits set to 0 the host part.