[libvirt-users] Questions on using bridge for KVM on ubuntu 13.10

Hi, I have being try to connect a virtual machine to the outside through a bridge on the host. The following shows that I have a bridge. And I'm able to start a guest. pengy@rigel:~$ brctl show bridge name bridge id STP enabled interfaces br0 8000.c81f66e29049 no em4 br1 8000.c81f66e29045 no bond0 virbr0 8000.000000000000 yes pengy@rigel:/mnt/nfs/pengy/kvm$ virsh create saiph_installed.xml Domain saiph created from saiph_installed.xml pengy@rigel:/mnt/nfs/pengy/kvm$ brctl show bridge name bridge id STP enabled interfaces br0 8000.c81f66e29049 no em4 vnet0 br1 8000.c81f66e29045 no bond0 virbr0 8000.000000000000 yes I assigned the static ip address (given my our network administrator) to the guest. But I am not able to connect anywhere outside from the guest (175.91.244.74). Do you know what might cause the problem? How to connect the outside network from the guest? Thanks. pengy@rigel:/mnt/nfs/pengy/kvm$ ssh 175.91.244.74 pengy(a)175.91.244.74's password: Welcome to Ubuntu 13.10 (GNU/Linux 3.11.0-12-generic x86_64) * Documentation: https://help.ubuntu.com/ System information as of Tue Mar 11 14:04:07 CDT 2014 System load: 0.0 Processes: 76 Usage of /: 78.0% of 999MB Users logged in: 0 Memory usage: 1% IP address for eth0: 175.91.244.74 Swap usage: 0% Graph this data and manage this system at: https://landscape.canonical.com/ 0 packages can be updated. 0 updates are security updates. Last login: Tue Mar 11 14:04:07 2014 pengy@saiph:~$ ping www.google.com ^C pengy@saiph:~$ ifconfig eth0 Link encap:Ethernet HWaddr 52:54:aa:00:f0:51 inet addr:175.91.244.74 Bcast:175.91.247.255 Mask:255.255.248.0 inet6 addr: fe80::5054:aaff:fe00:f051/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:6720 errors:0 dropped:24 overruns:0 frame:0 TX packets:213 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:513702 (513.7 KB) TX bytes:20976 (20.9 KB) lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:65536 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:0 (0.0 B) TX bytes:0 (0.0 B) BTW, I'm albe to follow some of the instructions at http://wiki.libvirt.org/page/Networking#Debian.2FUbuntu_Bridging But it is not clear to what the followings are for. net.bridge.bridge-nf-call-ip6tables = 0 net.bridge.bridge-nf-call-iptables = 0 net.bridge.bridge-nf-call-arptables = 0 *** Sample rc.local file *** /sbin/sysctl -p /etc/sysctl.conf iptables -A FORWARD -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --clamp-mss-to-pmtu exit 0 To verify that the changes have taken affect, please run tail /proc/sys/net/bridge/* iptables -L FORWARD -- Regards, Peng