Virtual Machine routing On Ubuntu
charlescurley at charlescurley.com
Sun Jun 20 14:37:24 MDT 2010
Grumble. I found out that while I can ping from one VM to another I
can't ssh. I also need to use arbitrary ports above 1024.
On Sat, 19 Jun 2010 01:40:32 -0600
Mike Lovell <mike at dev-zero.net> wrote:
> are you using a gui or wrapper around libvirt to manage your VMs or
> are you using the libvirt tools directly?
Wrapper, probably virt-manager 0.7.0-3ubuntu1.
> can you see the XML domain
> definitions for the VMs?
I see /etc/libvirt/qemu/<hostname>.xml and they sure look like
> if so, how is the networking configured for
> the VMs and on the host?
This looks like the relevant stanza:
> what is the full command line that was used
> to invoke the qemu process? `cat /proc/<pid of vm qemu
> process>/cmdline` to get that.
Hmm, it looks like it's KVM, rather than qemu.
root at dzur:~# cat /proc/7350/cmdline
/usr/bin/kvm-S-Mpc-0.11-m512-smp1-namecopper-uuidcfc4cc11-6518-28d6-0ac8-b2bb1cc2836d-monitorunix:/var/run/libvirt/qemu/copper.monitor,server,nowait-bootd-drivefile=/var/lib/libvirt/images/copper.img,if=ide,index=0-drivefile=/var/lib/libvirt/images/SLES-11-SP1-DVD-i586-GM-DVD1.iso,if=ide,media=cdrom,index=2-netnic,macaddr=54:52:00:5c:d1:f5,vlan=0,name=nic.0-nettap,fd=18,vlan=0,name=tap.0-serialpty-parallelnone-usb-vnc127.0.0.1:0-ken-us-vgacirrus-soundhwes1370root at dzur:~#
> as i understand it, the difference between a 'NAT' configuration and
> a 'host-only' configuration is that the necessary stuff for the host
> to perform NAT is done during the network configuration where
> host-only doesn't. so in host-only, there are no routes configured
> for the vms to reach outside networks automatically.
Ah. So NAT is the way to go most of the time. Thanks.
> from your description, it almost sounds like you are configuring
> multiple networks. one for each vm and then doing routing on the host
> between the vms. if this is how it is done, is ip forwarding enabled
> on the host? `cat /proc/sys/net/ipv4/ip_forward` to check. it sounds
> like it might not be since you are having trouble getting to the
> outside world from your vms. my next guess would be that there are
> rules in the iptables firewall that are preventing FORWARD traffic
> from getting between the hosts.
root at dzur:~# cat /proc/sys/net/ipv4/ip_forward
root at dzur:~#
However, writing a one to it made no difference.
> these links may also help you in your quest.
> hope that helps
Thanks. I'm slowly getting further with this.
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