From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ron Vachiyer Subject: Stripped 802.1q from frames Date: Fri, 09 Aug 2013 16:47:19 -0400 Message-ID: <52055557.5060701@abacom.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit To: KVM devel mailing list Return-path: Received: from tohs.cconn.info ([66.129.131.243]:54723 "EHLO tohs.cconn.info" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1031355Ab3HIWk3 (ORCPT ); Fri, 9 Aug 2013 18:40:29 -0400 Received: from [IPv6:2605:2a00:ffff:fffe:1de7:89b3:c9bd:6344] ([IPv6:2605:2a00:ffff:fffe:1de7:89b3:c9bd:6344]) (authenticated bits=0) by tohs.cconn.info (8.14.4/8.14.4) with ESMTP id r79KlCFo015206 (version=TLSv1/SSLv3 cipher=DHE-RSA-CAMELLIA256-SHA bits=256 verify=NO) for ; Fri, 9 Aug 2013 16:47:12 -0400 Sender: kvm-owner@vger.kernel.org List-ID: Hello, I have a curious behaviour I am seeing on my two KVM hosts running under CentOS6.4 on HP Hardware (bnx2 NICs in both cases), virtio is configured for the guest networking. The hosts are connected to Cisco switches on a trunk port. I have noted that flooded frames from 802.1q VLANs not native to any interface on the KVM hosts are stripped of their 802.1q tags and forwarded to guests configured to use the bridge0 or macvtap interface on the host (whatever native VLAN that host is in). KVM guests that are utilizing a different 802.1q-tagged bridge interface on the host do not see this behaviour. At first I believed it was an issue with the host that was bonding two NICs, however the second host on a single eth0 interface is seeing the same thing. I have run a packet capture on a guest and the host simultaneously and confirmed that although the host will receive a frame from the Cisco switch tagged for example VID:08, for which the kvm host does not have an interface, libpcap shows the 802.1q tag on the frame. However, that very same frame somehow gets stripped of that tag, and the guest has visibility to this frame but without the tag. I first noticed this when a guest I was installing using SLAAC autoconfigured itself with a IPv6 address from another VLAN not configured on the KVM host. Google has not shown me any links to this, therefore could this be a configuration snafu or is there somewhere else I could look to fix this? Thanks, Ron.