Two ways to represent addressing:

 

• Decimal: 255.255.255.225
• Binary: 11111111. 11111111. 11111111. 11111111

 

Hex is also used in some cases, such as in the Windows Registry to store the local machine's IP

 

 

 

IP Address Classes

 

There are 5 classes of IP addresses, three of which you will commonly encounter when working with network equipment:

 

1. Class A
2. Class B
3. Class C
4. Class D
5. Class E

 

Class D is used for multicasts and Class E is reserved for research purposes.

With some exceptions, Class A, B, and C addresses are routable and are the types of IP addresses you will most commonly encounter.

Overview of Class A, B, and C

 

- Class A = Network.Host.Host.Host

- Class B = Network.Network.Host.Host

- Class C = Network.Network.Network.Host

Two ways to identify which Class an IP address falls into, both dealing with the first octet:

1. Memorize all the address ranges for all three classes
2. Convert the first octet to binary
    
   Class A
    
   Range: 0-127
   First Octet: 0xxxxxxx
    
   Class B
    
   Range: 128-191
   First Octet: 10xxxxxx
    
   Class C
    
   Range: 192-223
   First Octet: 110xxxxx

Special IP addresses and Ranges 

• Non Routable networks

Also known as private internets, defined in RFC 1918

-Class A = 10.0.0.0 - 10.255.255.255

-Class B = 172.16.0.0 - 172.31.255.225

-Class C = 192.168.0.0 - 192.168.255.255

• All 0 network bits - this network
• All 1 network bits - all networks
• 127.0.01 = loopback
• All 0 host bits = this host
• All 1 host bits = all hosts on the specified network
• All 0 = Default route
• All 1 = Broadcast to all nodes on current network

 

Subnetting

 

Why in the world would you want to do this?

IP addresses are doled out by the network, not per IP.

Subnetting allows you do divide up an allotted network into smaller, routable, and more manageable networks.

 

Default masks:

- Class A = 255.0.0.0

- Class B = 255.255.0.0

- Class C = 255.255.255.0

 

Great tutorial : http://www.ralphb.net/IPSubnet

How to:

 

Binary Method:

1. Split the Host Bits into subnet and host bits. There must be at least 2 subnet bits, and they can't be all OFF or all ON for a valid subnet (unless there is no subnet/default mask)
2. The next number after the subnet is the first valid host
3. the second to last number before the next (valid or invalid) subnet is the last valid host
4. the broadcast address is the last number before the next (valid or invalid) subnet.

 

Example:

 

255.255.255.192 - as a class C subnet mask

 

• 192 = 11000000
• all possible subnet combos: 00, 01, 10, 11
• valid combos: 01, 10

 

 

 

Non-Confusing mechanical method

1. Number of subnets = 2^x-2, where x is the number of ON bits
2. Hosts per subnet = 2^y-2, where y is the number of OFF bits
3. Valid Subnets? 256-subnet mask = base number
4. Valid Hosts? Numbers between the subnets, non counting all 0's and all 1's
5. Broadcast? All host bits ON, or number before the next subnet

 

Examples:

 

255.255.255.192 as a Class C mask

 

1. 2
2. 62
3. 256-192= 64 is base. 64+64=128, 128+64=192=mask, so stop here and don't use last result
4. 65-127, 129-190
5. broadcasts = 127, 191

 

255.255.255.224 as a class C

• 224 = 11100000
• 3 subnet bits

1. 6
2. 30
3. 256-224=32 the base, you can do the math...
4. 33-62, ...
5. 63, ...

 

255.255.192.0 as a class B

 

1. 2
2. 16382
3. 64
4. 64.1-127.254, 128.1, 191.254
5. 127.255, 191.255

 

255.255.255.128 as a Class B

• 255 = 11111111
• 128 = 10000000

1. 2⁹-2 = 510
2. 2⁷-2 = 126
3. 256-255 = 1, plus you get another subnet for each third octet value due to the 1 fourth octet value, thus 0.128, 1.0, 1.128, ...
4. ...

 

Network Design

 

Core Layer - High Speed Connectivity Layer

Distribution Layer - Routing decisions and network policies

Access Layer - Connectivity into the network