iptables and /32 vs /24

[Steve Wolf]

I have taken a course on IP numbers etc. but I dont recall. (ok it was years ago) what /32 means.

If i issue the command

 

/sbin/iptables -A INPUT -s 69.212.12.76/32 -j DROP
Vs

/sbin/iptables -A INPUT -s 69.212.12.76/24 -j DROP

Or even

/sbin/iptables -A INPUT -s 69.212.12.76 -j DROP

I think /32 based on an ip calculator is only that IP?

Right ??

 

/24 of course means from 10.1.0.1 to 10.1.0.254

 

And of course no ending just means that specific ip.

 

Can anyone confirm if Im right or if Im off base. I also asume that any of these syntaxes are acceptable depending on what you want.

 

Thanks.

 

[Bryan Smith]

Hey,

The /24 is incorrect, the last number must be a 0 like 69.212.12.0/24 for a 256 ip block starting from 69.212.12.0 to 69.212.12.255

I'd do this way:

/sbin/iptables -A INPUT -s 69.212.12.0/24 -j DROP

/sbin/iptables -A INPUT -s 69.212.12.76 -j DROP

The /32 is indeed only for that ip so it's really pointless to add the /32 on there. Fix the /24 and then you're ready to roll. 

Bryan

 

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[Steve Wolf]

Great thanks. Thats helpfull.

Regards