Need to block ?

Adalbert Prokop adalbert.prokop at gmx.de
Sat Jun 30 12:40:55 UTC 2007


Bob Goodwin - W2BOD wrote on Saturday 30 June 2007:

> What is the correct notation for blocking a range of addresses in my
> router?

> If I block 64.18.5.13  it simply moves up to 64.18.5.14.

> I thought the proper way to do it was 64.18.5.0/255 but obviously
> that's wrong or at least doesn't work for me.

You are mixing up mask notations. There are two of them

1) dottet decimal notation, like 255.255.255.0
2) CCIT notation, like 192.168.1.0/24

192.168.1.0/24 says "the first 24 bits of the mask are ones" and is 
255.255.255.0 in decimal notation.

255.255.255.0 = 11111111 11111111 11111111 00000000
                --------------------------
                         24 ones

What you said was "the first 255 bits of the mask are ones" and that is 
nonsense, since the mask is only 32 bit long (4 bytes).

CCIT notation is a little more limited than dottet notation, since you 
cannot create a mask like 

11111111 11111111 10101010 00000000 = 255.255.170.0

But in practice it is irrelevant, since there is (almost?) no reason to 
use such masks.

-- 
bye,
Adalbert

pseudo-user on a pseudo-terminal




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