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how can I find Net mask address in the rage: 192.16.128.0 to 192.16.135.255 Note: I want to use Classless Inter-Domain Routing so net mask should not be multiple of 8. what should we calculate it for every different range ?

Ryan Foley
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user5716
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1 Answers1

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If you write those addresses in binary, you get:

11000000 00010000 10000000 00000000 = 192.16.128.0
11000000 00010000 10000111 11111111
| ----- 21 bits ----- |

Since the addresses have the same first 21 bits, the mask is then /21 (255.255.248.0) .

Otherwise you can do it in the head for simple case: x.x.x.0-255 is /24, two of those networks (starting on an even number) are /23, 4 are /22, 8 are /21 (135-128=8).

mulaz
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