A Simplified Tutorial
COMPAS ID 92962
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• LANs and VLANs: A Simplified Tutorial
The purpose of this tutorial is to give the newcomer to data networking a basic understanding of IP addressing. The following topics are covered.
IP addressing fundamentals
Classful IP addressing
Variable length subnet masks (VLSM)
Classless inter-domain routing (CIDR)
Routing and routing protocols
IP Addressing Fundamentals
OSI and TCP/IP
7 – Application
6 – Presentation
5 – Session
4 – Transport
3 – Network
2 – Data Link
1 – Physical
Terms used in this tutorial
Host – to – Host
TCP port, UDP port
• This table is presented for reference purposes.
– The first column shows the 7-layer OSI Reference Model, which is a model used to design protocols that make networking possible.
– The second column shows the TCP/IP protocol stack in reference to the OSI model. TCP/IP is the prevalent protocol stack for data networking. – The third column shows that an IP address is a layer 3 (L3) address, as well as its relationship to the MAC address and TCP/UDP port, which are not covered in this tutorial.
Anatomy of an IP address
• The IP address is a 32-bit address that consists of two components. • One component is the network portion of the address, consisting of the network bits.
– The network bits make up the left portion of the address. – They consist of the first bit up to some boundary, to be discussed later.
• The second component is the host portion of the address, consisting of the host bits.
– The host bits make up the right portion of the address.
– They consist of the remaining bits not included with the network bits.
• The network portion of the address is separated from the host portion of the address by a mask.
• The mask simply indicates how many bits are used for the network portion, leaving the remaining bits for the host portion.
• A 24-bit mask indicates that the first 24 bits of the address are network bits, and the remaining 8 bits are host bits.
• A 16-bit mask indicates that the first 16 bits of the address are network bits, and the remaining 16 bits are host bits.
• And so forth…
• The difference between a network mask and a subnet mask will be explained as this tutorial progresses.
Quick lesson in binary math
• Binary math is based on powers of 2, as opposed to powers of 10 for decimal math.
– Whereas decimal math has a 1s place, 10s place, 100s place, and so forth… – Binary math has a 1s place, 2s place, 4s place, 8s place, and so forth.
• Given an octet (8 bits), when a bit in the octet is set (1) its value is… –
128 = left-most bit (most significant bit) = 27
64 = next bit = 26
32 = next bit = 25
16 = next bit = 24
8 = next bit = 23
4 = next bit = 22
2 = next bit = 21
1 = right-most bit (least significant bit) = 20
• When a bit in an octet is not set (0) its value is zero. • The decimal value of an octet is the sum of each set bit’s value. – 11000000 = 128 + 64 = 192
– 10101000 = 128 + 32 + 8 = 168
– 11111111 = 128 + 64...
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