From owner-freebsd-net Fri Oct 19 2:13:31 2001 Delivered-To: freebsd-net@freebsd.org Received: from mailhub.fokus.gmd.de (mailhub.fokus.gmd.de [193.174.154.14]) by hub.freebsd.org (Postfix) with ESMTP id 2027F37B403; Fri, 19 Oct 2001 02:13:23 -0700 (PDT) Received: from beagle (beagle [193.175.132.100]) by mailhub.fokus.gmd.de (8.8.8/8.8.8) with ESMTP id LAA26862; Fri, 19 Oct 2001 11:12:48 +0200 (MET DST) Date: Fri, 19 Oct 2001 11:12:48 +0200 (CEST) From: Harti Brandt To: Terry Lambert Cc: "Jose M. Alcaide" , Beech Rintoul , , Subject: Re: arp: is using my IP address 0.0.0.0! ??!?!? In-Reply-To: <3BCEEBDD.46121235@mindspring.com> Message-ID: <20011019110116.Y1072-100000@beagle.fokus.gmd.de> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-freebsd-net@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.org On Thu, 18 Oct 2001, Terry Lambert wrote: TL>To expand a little... TL> TL>> That said, it's probably a good idea to never ARP for 0.0.0.0, TL>> since a "who has" in that case is a really dumb idea, since, TL>> as weas pointed out, it's intended to mean "this host", in the TL>> absence of an IP address (i.e. 0.0.0.0 is not an IP address, TL>> it's a special value meaning "not an IP address"). TL> TL>It's probably also a good idea to make interfaces who have an TL>IP of 0.0.0.0 _not_ respond to ARP requests for that address, TL>and, just in case there are other idiots, we should also not TL>give proxy ARP responses for that address, etiher. I have run tcpdump all night to find out what happens. The host receives an ARP request with a source address of 0.0.0.0: 18:33:51.222688 arp who-has hydra tell 0.0.0.0 0001 0800 0604 0001 0030 65c6 a174 0000 0000 0000 0000 0000 c1af 8755 5555 5555 5555 5555 5555 5555 5555 5555 5555 I think, this may happen if the host does not yet know it's IP address (DHCP maybe?). But FreeBSD-current for some unknown reason answers to this request: 18:33:51.222835 arp reply 0.0.0.0 is-at 0:60:97:a:99:f 0001 0800 0604 0002 0060 970a 990f 0000 0000 0030 65c6 a174 0000 0000 5555 5555 5555 5555 5555 5555 5555 5555 5555 and then prints: Oct 18 18:33:51 scotty /boot/kernel/kernel: arp: 00:30:65:c6:a1:74 is using my IP address 0.0.0.0! I think this is because I have an interface that is up and has NO IP address: lo0: flags=8049 mtu 16384 inet 127.0.0.1 netmask 0xff000000 xl0: flags=8943 mtu 1500 inet 193.175.135.70 netmask 0xffffff00 broadcast 193.175.135.255 ether 00:60:97:0a:99:0f media: Ethernet 10baseT/UTP (10baseT/UTP ) hatm0: flags=841 mtu 9180 media: ATM UTP/155MBit status: active lane0: flags=8802 mtu 1516 ether 00:00:00:00:00:00 I think it is definitly wrong to assume that an interface with no IP address has IP address 0.0.0.0 harti TL>Ghah. I hate special cases... everything is a special case... harti TL> TL>-- Terry TL> TL>To Unsubscribe: send mail to majordomo@FreeBSD.org TL>with "unsubscribe freebsd-net" in the body of the message TL> -- harti brandt, http://www.fokus.gmd.de/research/cc/cats/employees/hartmut.brandt/private brandt@fokus.fhg.de To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message