Policy Misunderstanding: RTFM Guidance Requested.

Mike 1100100 at gmail.com
Wed Sep 1 20:12:56 CEST 2004

> Better to let things through the mangle and nat tables, and do filtering in
> the filter table.  There have been folks who like to drop things in the
> mangle and nat tables, but setting actual DROP policies makes life very
> difficult.

This seems like sound advice after what I've been through.  Maybe the
folks in The Matrix can bend the laws of physics with relative ease,
but for myself, I can barely achieve 'dude' status.  I think I'll
ACCEPT mangle and nat, and get some sleep tonight.  :-)

>         There is no definition of the SOURCE that you want to drop ICMP echorequests
> from.  Thus this rule drops all ping echorequests.
>         iptables -t filter -A INPUT -p icmp -i [internet pipe device] -icmp-type \
> echo-request -j DROP
>         will allow your LAN users to ping the box, but prevent pings from the
> internet from getting in.

Oh I see.  By stating specifically the internet-facing device, you
make it possible for LAN clients to ping the box through the gateway
NIC - eth1, while the rule blocks all the other echo requests.

>         Really and truely -- Oskar's tutorials are great and easy to read... and even
> the sample firewalls there are decent enough to start with for a newbie.
I definitely feel more secure about working on my firewall knowing
that this reference material is around.  It's packed.

Thanks again, Alistair.
It's great to have your assistance.


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