From owner-freebsd-isp Mon Sep 25 6:10: 6 2000 Delivered-To: freebsd-isp@freebsd.org Received: from velvet.sensation.net.au (serial1-2-velvet-brunswick.sensation.net.au [203.20.114.195]) by hub.freebsd.org (Postfix) with ESMTP id ECFA237B424 for ; Mon, 25 Sep 2000 06:09:55 -0700 (PDT) Received: from localhost (rowan@localhost) by velvet.sensation.net.au (8.9.3/8.9.3) with ESMTP id AAA32011 for ; Tue, 26 Sep 2000 00:09:59 +1100 (EST) (envelope-from rowan@sensation.net.au) X-Authentication-Warning: velvet.sensation.net.au: rowan owned process doing -bs Date: Tue, 26 Sep 2000 00:09:57 +1100 (EST) From: Rowan Crowe To: freebsd-isp@freebsd.org Subject: Re: what is icmp src 8 dst 0? In-Reply-To: Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-freebsd-isp@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.org On Mon, 25 Sep 2000, Leif Neland wrote: > Last week I aired a problem where some hosts were unable to reach another > in 80% of the time. > > It has now been determined that the almost unreachable server is behind a > firewall, which doesn't like being sent icmp's with src port 8 to dst port > 0, their consultant said. When it recieves such a packet, the firewall > "hides itself" from all packets from that destination in 20 minutes. > > So the question is "what is icmp src 8 dst 0"? He probably means ICMP type 8 code 0, which is an echo request (ping). ICMP does not have a concept of port numbers. An ICMP echo request is pretty harmless, so it must be a real paranoid firewall... > Is it a "legal" request? > > The source machines are running squid. Have a look in squid.conf for "ping", "pinger" and "icmp", that may give you some clues... from a quick look, it's something to do with measuring the number of hops and network latency to a host (parent/sibling?) which is used in the selection of who to fetch from. It doesn't appear to be on by default, so it's been specifically compiled in by someone. Cheers. -- Rowan Crowe http://www.rowan.sensation.net.au/ Sensation Internet Services http://info.sensation.net.au/ Melbourne, Australia Phone: +61-3-9388-9260 To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-isp" in the body of the message