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How to define a rule in Windows server 2008 firewall to be applied to an IP range. For example blocking IPs which start with 202 I mean all IPs which meet 202...*

There are two options when creating a new rule:

  1. This IP address or subset:

  2. This IP address range:

How should I define such a wide range ?

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migrated from superuser.com Nov 9 '11 at 1:28

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That is the range between 202.0.0.0 to 202.255.255.255. I assume that you mean IPv4. –  soandos Aug 2 '11 at 17:23
    
I'd first ask the question, "why are you blocking all those IPs in the first place?" A blanket answer wouldn't fit here, nor would it be beneficial to you in the long term. –  surfasb Aug 2 '11 at 17:24
    
Yes I mean IP v4. I was wondering if this wide range has a negative performance issue or not. –  Xaqron Aug 2 '11 at 17:25
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1 Answer

up vote 0 down vote accepted

The range begins at 202.0.0.0 and ends at 202.255.255.255. You can also represent it as 202.0.0.0/8.

Why /8?

An IPv4 address is a 32-digit binary number that has been conveniently divided into 4 groups. The address 202.0.0.0 expressed in binary is

11001010 00000000 00000000 00000000

In this context /8 means "match the first 8 binary digits", or any address that begins with 202..

Read all about it at the Wikipedia article for Classless Inter-Domain Routing.

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Why 202.0.0.0/8 ? What does 8 mean here ? –  Xaqron Aug 2 '11 at 17:54
    
@Xaqron I updated my answer to address your question. –  William Jackson Aug 2 '11 at 18:28
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