Thanks fo the reply... I noticed the error of the "/32" CIDR right after I
sent it.
Brain fart on my part.
I just wanted to know if
218.0.0.0 without the" /*" would work. (blocking the whole 218.0.0.0
block)
From: "/dev/rob0" <rob0@xxxxxxxxx>
To: <netfilter@xxxxxxxxxxxxxxxxxxx>
Sent: Saturday, June 18, 2005 12:46 PM
Subject: Re: What's the best way to block these IP's?
On Saturday 18 June 2005 11:46, Netfilter wrote:
What's the best way to block these IP's?
I'm not sure what your question is. I see a few main possibilities
about which you might be asking. I'll address those.
-A INPUT -p tcp -s 213.0.0.0/32 -i eth1 -j DROP
or
-A INPUT -p tcp -s 218.0.0.0 -i eth1 -j DROP
Maybe you don't understand CIDR notation, and thus don't know what
these do. A /32 netmask means "this IP only" in English. 32 bits of
netmask is 255.255.255.255. Both forms are the same!
If you want to block all IP's starting with 213 or 218, those won't do
it. You would need to use /8 or smaller. 218.0.0.0/8 is 218.0.0.0
through 218.255.255.255; 218.0.0.0/7 is 218.0.0.0 through
219.255.255.255. Rusty's Networking Concepts HOWTO might help.
Generally the best strategy for firewalling is to choose what to allow
and let everything else hit a DROP or REJECT policy or rule. Here the
Packet Filtering HOWTO has examples which might help. Note as well that
all your examples are only limiting TCP traffic, and only if coming in
your eth1 interface.
Furthermore there are common misunderstandings concerning the role of
INPUT as opposed to FORWARD. If you're wanting to block traffic from or
to NAT users, your INPUT rules will not do it. Again this is explained
in the Packet Filtering HOWTO.
When I have common rules I want called from both INPUT and FORWARD, I
use a new chain ...
# iptables -N Common
# iptables -vA Common -s 218.0.0.0/7 -j DROP
[ ... other rules as wanted ... ]
# iptables -vA INPUT -j Common
# iptables -vA FORWARD -j Common
You can of course limit the type of traffic sent to the chain with
matches on the calling rule.
HTH, and if not you, HTH someone else.
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