[Users] Networking problem inside a openvz virtual machine

Kristian F. Høgh kfh at segtel.dk
Thu Jun 12 06:49:19 EDT 2008

On Thursday den 12. June 2008 12:15:24 Michael Schwartzkopff wrote:
> Hi,
> I want to setup a Linux-HA cluster inside a vitual openvz machine. Due to
> the nature of openvz virtual machines I have a problem with IP address
> resources.
> Let me explain the problem: Inside openvz virtual machine there are two
> different network devices venet and veth.
> As far as I understood the documentation, using venet devices you cannot
> change the ip address inside the virtual machine. So no chance to set up a
> cluster using IPaddr2 resource the easy way. So no chance to let heartbeat
> control the IP adress here.I have a ugly workaround, but  that is not the
> topic here.
> Using veth device you can change the IP address inside the virtual machine.
> But  you have to set up proxy arp on the host machine and also the host has
> to know about routing to that machine.

I don't use HA nor venet, but anyway...
I setup bridge (br0) in VE0, and attach physical network adapter to it.

When I start a VE (ID: 1000), I create a veth pair.
In VE0 called ve1000.0 and in VE1000 called eth0.

I attach ve1000.0 to br0 in script pointed to by EXTERNAL_SCRIPT= 
in /etc/vz/vznet.conf
Then there is no need for proxy arp.

The VE itself configures the IP address on eth0.

> If the IP address resource inside 
> the virtual machine is moved away to an other virtual machine located on
> the same host or another one, the original host will still advertise its
> MAC address for the vitual IP adress of the cluster and will route the
> packets to the virtual machine not serving the IP address any more.
> Did I understand OpenVZ documentation right?
> Is there any way out of this dilemma using heartbeat inside openvz vitual
> machines?

I assume you can create secondary IP address on eth0 in VE1000.

> Greetings,

Good luck,
Kristian Høgh

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