Hello list, We have KVM setup using libvirt (0.9.0) as configuration device on a Debian Squeeze Host. Networking is done in routed bridge mode and we have two different subnets, as well as one main ip. Subnets get routed to the main ip (this is done by our provider). Network on hosts are done like this: <network> <name>subnet_1</name> <uuid>7c60990d-ab31-c4a5-cd2b-5ce4c7c61d38</uuid> <forward dev='eth0' mode='route'/> <bridge name='virtbridge1' stp='off' delay='0' /> <mac address='52:54:00:4D:83:2A'/> <ip address='xx.xx.240.121' netmask='255.255.255.248'> </ip> </network> <network> <name>subnet_2</name> <uuid>7c60990d-ab31-c4a5-cd2b-5ce4c7c61d38</uuid> <forward dev='eth0' mode='route'/> <bridge name='virtbridge1' stp='off' delay='0' /> <mac address='52:54:00:4D:83:2A'/> <ip address='xx.xx.240.200' netmask='255.255.255.248'> </ip> </network> Routing on host Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface xx.xx.122.33 0.0.0.0 255.255.255.255 UH 0 0 0 eth0 xx.xx.240.120 0.0.0.0 255.255.255.248 U 0 0 0 virtbridge1 xx.xx.239.200 0.0.0.0 255.255.255.248 U 0 0 0 virtbridge2 0.0.0.0 xx.xx.122.33 0.0.0.0 UG 0 0 0 eth0 Guests get this: <interface type='network'> <mac address='de:ad:b6:83:85:5b'/> <source network='subnet_1'/> <model type='virtio'/> <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'/> </interface> Guests put this into interfaces: iface eth0 inet static address xx.xx.239.202 netmask 255.255.255.248 gateway xx.xx.239.201 Guest routing Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface xx.xx.239.200 0.0.0.0 255.255.255.248 U 0 0 0 eth0 0.0.0.0 xx.xx.239.201 0.0.0.0 UG 0 0 0 eth0 Everything seemed to work just fine, that is: Guests could connect - to host, - to internet - to other virtual maschines in the same subnet - all vice-versa. Internet can connect to any guest and our host can connect to any guest, too. Then, we needed one guest to connect to a guest from the other subnet. And this does not work, what I get follows: PING xx.xx.240.122 (xx.xx.240.122) 56(84) bytes of data. > From xx.xx.239.201 icmp_seq=1 Destination Port Unreachable > From xx.xx.239.201 icmp_seq=2 Destination Port Unreachable Note, that I can ping the other subnets gateway just fine! But I cannot connect to any of the other subnet IPs. I believe this is just a routing problem, but I cannot figure out what route to add where. Please ask if you need any more information.