Ping With Iptables.

Ping With Iptables.

[Hélio Dubeux]

Hi, everybody. This is my first message here and i hope you can help me.
I have a Linux Box as a Gateway of my network. And i want do allow internal 
machines to ping the Internet but i also want to block external machines to 
ping my Gateway. Is this is possible plz send me something... Thanx.

----------------------
Hélio Dubeux Neto




_________________________________________________________________
MSN Hotmail, o maior webmail do Brasil. http://www.hotmail.com

Re: Ping With Iptables.

[Walther]

set your default policy to drop and allow forwarding icmp-echo-request and 
icmp-echo-reply from your local lan:

<--snip-->

iptables -P INPUT DROP
iptables -P OUTPUT DROP
iptables -P FORWARD DROP

iptables -A FORWARD -i $INT -o $EXT -p icmp --icmp-type echo-request -j 
ACCEPT
iptables -A FORWARD -o $EXT -i $INT -p icmp --icmp-type echo-reply -j 
ACCEPT

<--snip-->

this should work

Best Regards,
MfG.

Stefan Walther
stefan_walther@gehag-dsk.de
dienst.: +4930/89786448
Funk: +49172/3943961
http://www.gehag-dsk.de

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Hélio Dubeux <hdubeux@hotmail.com>
Sent by: netfilter-admin@lists.netfilter.org
29.10.2002 14:51

 
        To:     netfilter@lists.netfilter.org
        cc: 
        Subject:        Ping With Iptables.


Hi, everybody. This is my first message here and i hope you can help me.
I have a Linux Box as a Gateway of my network. And i want do allow 
internal 
machines to ping the Internet but i also want to block external machines 
to 
ping my Gateway. Is this is possible plz send me something... Thanx.

----------------------
Hélio Dubeux Neto




_________________________________________________________________
MSN Hotmail, o maior webmail do Brasil. http://www.hotmail.com

Re: Ping With Iptables.

[Maciej Soltysiak]

Hello,

> I have a Linux Box as a Gateway of my network. And i want do allow internal
> machines to ping the Internet but i also want to block external machines to
> ping my Gateway. Is this is possible plz send me something... Thanx.

#let the internal net ping the world
iptables -A FORWARD -p icmp -s $YOUR_NET -j ACCEPT

#disallow the world to ping the gateway
iptables -I INPUT -p icmp -d $GATEWAY_IP -j DROP

Of course this is very rough, i do not know your rulesets, it is possible
that it can be done better to suit your current chains and rules.

Note, the -I INPUT - if we have other icmp rules, they may ACCEPT the
pings earlier than if we had just appended the rule, hence we're
inserting.

Re: Ping With Iptables.

[Antony Stone]

On Tuesday 29 October 2002 3:34 pm, Maciej Soltysiak wrote:

> Hello,
>
> > I have a Linux Box as a Gateway of my network. And i want do allow
> > internal machines to ping the Internet but i also want to block external
> > machines to ping my Gateway. Is this is possible plz send me something...
> > Thanx.
>
> #let the internal net ping the world
> iptables -A FORWARD -p icmp -s $YOUR_NET -j ACCEPT
>
> #disallow the world to ping the gateway
> iptables -I INPUT -p icmp -d $GATEWAY_IP -j DROP
>
> Of course this is very rough, i do not know your rulesets, it is possible
> that it can be done better to suit your current chains and rules.

I would instead recommend
iptables -P INPUT DROP

and then only add rules for the things you really do want to come in to the 
firewall (established & related is probably a good start).

"Allow what you know you want, and drop everything else" is a good policy.

Antony.

-- 

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!X- !R K--?

Re: Ping With Iptables.

[Maciej Soltysiak]

> I would instead recommend
> iptables -P INPUT DROP
>
> and then only add rules for the things you really do want to come in to the
> firewall (established & related is probably a good start).
Well of course, i wrote that, keeping in mind that he could have other
rules like:
-s 0/0 -j ACCEPT

> "Allow what you know you want, and drop everything else" is a good policy.
Is the best in most cases.

> Antony.
Maciej