From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Ron Watkins" Subject: Re: ARP problems in -testing? Date: Mon, 17 Jan 2005 05:39:44 -0500 Message-ID: <003e01c4fc80$dbc1c860$32dcdc0a@vanish> References: <41EB0678.4070707@devrandom.net> Mime-Version: 1.0 Content-Type: text/plain; format=flowed; charset="iso-8859-1"; reply-type=response Content-Transfer-Encoding: quoted-printable Return-path: Sender: xen-devel-admin@lists.sourceforge.net Errors-To: xen-devel-admin@lists.sourceforge.net List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , List-Archive: To: xen-devel@lists.sourceforge.net List-Id: xen-devel@lists.xenproject.org I. Am. An. Idiot. Thanks, Derrick. <> ----- Original Message -----=20 From: "Derrik Pates" To: "Keir Fraser" Cc: "Jan Kundr=E1t" ; "Ron Watkins" ;=20 Sent: Sunday, January 16, 2005 7:27 PM Subject: Re: [Xen-devel] ARP problems in -testing? > Keir Fraser wrote: >> The MAC addresses from the tcpdump log look sane. The problem must lie >> elsewhere. > > I just tried this on a dedicated server located at thePlanet in Texas; = I=20 > think this is an issue that combines the following: > > - No MAC address specified causes a random MAC address to be selected= at=20 > domain create time > - The upstream router has a local ARP cache > - The host system's ARP cache for addresses on the virtual NIC for th= e=20 > instance is blown out when the virtual interface disappears when the=20 > domain is destroyed > > This seems to explain why tcpdump shows packets going to the VM's IP, b= ut=20 > TCP sessions and ICMP packets don't get a response - the switch still=20 > knows the "old" MAC address, but the first outbound packet to the outsi= de=20 > world implicitly eradicates the old ARP-cache entry. I don't think this= is=20 > Xen's fault at all, just a property of the implementation of ARP=20 > resolution. I just happened to notice that the MAC shown in incoming=20 > packets didn't match the current MAC address (based on ifconfig's outpu= t),=20 > so this is my current theory on what's happening. > > --=20 > Derrik Pates > demon@devrandom.net > > > ------------------------------------------------------- > The SF.Net email is sponsored by: Beat the post-holiday blues > Get a FREE limited edition SourceForge.net t-shirt from ThinkGeek. > It's fun and FREE -- well, almost....http://www.thinkgeek.com/sfshirt > _______________________________________________ > Xen-devel mailing list > Xen-devel@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/xen-devel >=20 ------------------------------------------------------- The SF.Net email is sponsored by: Beat the post-holiday blues Get a FREE limited edition SourceForge.net t-shirt from ThinkGeek. It's fun and FREE -- well, almost....http://www.thinkgeek.com/sfshirt