From owner-freebsd-questions Mon Oct 7 7:10: 1 2002 Delivered-To: freebsd-questions@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 8486E37B401 for ; Mon, 7 Oct 2002 07:09:59 -0700 (PDT) Received: from rhadamanth.submonkey.net (pc1-cdif2-4-cust210.cdf.cable.ntl.com [80.4.10.210]) by mx1.FreeBSD.org (Postfix) with ESMTP id 81FFE43EA3 for ; Mon, 7 Oct 2002 07:09:58 -0700 (PDT) (envelope-from setantae@submonkey.net) Received: from setantae by rhadamanth.submonkey.net with local (Exim 4.10) id 17yYa5-000339-00 for freebsd-questions@FreeBSD.ORG; Mon, 07 Oct 2002 15:09:57 +0100 Date: Mon, 7 Oct 2002 15:09:57 +0100 From: Ceri Davies To: freebsd-questions@FreeBSD.ORG Subject: Re: block icmp with ipfw Message-ID: <20021007140957.GA11694@submonkey.net> References: <20021007093549.GA7137@submonkey.net> <200210071406.g97E6Nlc087362@lurza.secnetix.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <200210071406.g97E6Nlc087362@lurza.secnetix.de> X-message-flag: All your linuxconf-configured redhat are belong to us. User-Agent: Mutt/1.5.1i Sender: owner-freebsd-questions@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG On Mon, Oct 07, 2002 at 04:06:23PM +0200, Oliver Fromme wrote: > Ceri Davies wrote: > > add 00602 allow icmp from any to any icmptypes 8 out > > add 00603 allow icmp from any to any icmptypes 0 in > > ... > > default deny > > You should really do it the other way around: let all ICMP > types through, _except_ for those that you don't want (i.e. > ICMP ECHO). You will probably want several things to work > correctly which depend on ICMP, such as path MTU discovery > (RFC1191), detection of unreachable destinations or networks, > and similar things. ICMP means internet control message > protocol -- without it, several internet-related things just > don't work. Yes, I have separate rules for those. I should probably have stated this. > Personally, I wouldn't block ICMP at all, not even ICMP ECHO. > FreeBSD's ICMP bandwidth limit handles the usual situations > where you'd want to limit ICMP pretty well. I'd agree with this in most situations. The machine that those rules are from is unfortunately severly under-spec'd and overworked though, and I have found this makes a positive difference. Ceri -- you can't see when light's so strong you can't see when light is gone To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message