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5 Cards in this Set
- Front
- Back
- 3rd side (hint)
Subnet Classes
First octet ranges Subnet masks |
Class A
First octet: 1-126 Mask: 255.0.0.0 Class B First octet: 128-191 Mask: 255.255.0.0 Class C First octet: 192-223 Mask: 255.255.255.0 Class D First octet: 224-247 Class E First octet: 248-255 |
Classes are defined according to where the first zero bit is found in the first octet's four left most bits (first nibble).
In class A it is in the 7th bit. In class B it is in the 6th bit. In class C it is in the 5th bit. In class D it is in the 4th bit. In class E no zero bits in left most nibble. |
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Powers of 2
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2^0 = 1
2^1 = 2 2^2 = 4 2^3 = 8 2^4 = 16 2^5 = 32 2^6 = 64 2^7 = 128 2^8 = 256 2^9 = 512 2^10 = 1024 or 1K 2^11 = 2048 or 2K 2^12 = 4096 or 4K 2^13 = 8192 or 8K 2^14 = 16,384 or 16K 2^15 = 32,768 or 32K 2^16 = 65,536 or 64K |
X^0 is 1 for all values of X.
Each line is double the preceding line. |
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Formula to calculate number of hosts given number of host bits in the subnet
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2^n-2
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Where "n" is the number of host bits in the subnet
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Usable host addresses for host bits
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2 = 4-2 = 2
3 = 8-2 = 6 4 = 16-2 = 14 5 = 32-2 = 30 6 = 64-2 = 62 7 = 128-2 = 126 8 = 256-2 = 254 9 = 512 ~ 500 10 = 1024 ~ 1000 11 = 2048 ~ 2000 12 = 4096 ~ 4000 13 = 8192 ~ 8000 14 = 16,384 ~ 16,000 15 = 32,768 ~ 32,000 16 = 65,536 ~ 64,000 |
The right column can be added to the powers of 2 table for convenience.
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Class C Subnet masks, number of networks, number of hosts
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255.255.255.0 1 254
255.255.255.128 2 126 255.255.255.192 4 62 255.255.255.224 8 30 255.255.255.240 16 14 255.255.255.248 32 6 255.255.255.252 64 2 |
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