Hi, I am having an odd networking issue. It is one of those "it used to work, and now it doesn't" kind of things. I can't work out what I am doing differently. I have a virtual machine, started with (among other things): -net nic,macaddr=fa:9e:0b:53:d2:7d,model=rtl8139 -net tap,script=/images/1/ifup-eth0,downscript=/images/1/ifdown-eth0 -net nic,macaddr=fa:02:4e:86:ed:ce,model=e1000 -net tap,script=/images/1/ifup-eth1,downscript=/images/1/ifdown-eth1 The ifup-ethX script inserts the tap interface into the correct bridge (of which there are multiple.) The Virtual Machine is Centos 5.3, with a 2.6.27.21 kernel. The Host is Ubuntu 9.10 with a 2.6.31 kernel. My network then looks like: The Virtual Machine has an eth0 interface, which is matched with tap0 on the host. The Virtual Machine has an eth1 interface, which is matched with tap1 on the host. The host has a bridge br0, which contains tap0 and eth0. The host has a bridge br1, which contains tap1. There is a server on the same network as the Host's eth0. The Virtual Machines eth0 interface is down. The Virtual Machines eth1 interface has an IP address of 192.168.1.10/24. The Virtual Machine has a default gateway of 192.168.1.1. The host's br0 has an IP address of 192.168.0.1/24. The host's br1 has an IP address of 192.168.1.1/24. The server has an IP address of 192.168.0.20/24, and a default gateway of 192.168.0.1. Firewalling is disabled everywhere. I have allowed time for the bridges and STP to settle. If I go to the Virtual Machine, and ping 192.168.0.20 (the server), I would expect tcpdumps to show: * VM: eth1, dest MAC of Host's tap1/br0 * Host: tap1, dest MAC of Host's tap1/br0 * Host: br1, dest MAC of Host's tap1/br0 * Host now routes from br1 to br0 * Host: tap0, no packet * Host: br0, dest MAC of Server * Host: eth0, dest MAC of Server * Server: eth0, dest MAC of Server What I actually get: * VM: eth1, dest MAC of Host's tap1/br0 * Host: tap1, dest MAC of Host's tap1/br0 * Host: br1, dest MAC of Host's tap1/br0 * Host should, but does not route from br0 to br1 * Host: tap0, dest MAC of ***Host's tap1/br0*** * Host: br0, dest MAC of ***Host's tap1/br0** * Host: eth0, no packet * Server: eth0, no packet As you can see, the packet has egressed *both* tap interfaces! Is this expected behaviour? What can I do about this? If I remove tap0 from the bridge, I then get: * VM: eth1, dest MAC of Host's tap1/br0 * Host: tap1, dest MAC of Host's tap1/br0 * Host: br1, dest MAC of Host's tap1/br0 * Host should, but does not, route from br0 to br1 * Host: tap0, no packet * Host: br0, no packet * Host: eth0, no packet * Server: eth0, no packet This is the other half of my problem: in this case, with effectively only one tap, the host is not routing between br1 and br0. The packet just gets silently dropped. Does anyone know what I am doing wrong? I hope I have managed to explain this well enough! Thanks, -- Jarrod Lowe -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
