[CentOS-virt] understanding problems (was: Preferred method of provisioning VM images)

Fri Jun 13 16:33:29 UTC 2014
SilverTip257 <silvertip257 at gmail.com>

On Fri, Jun 13, 2014 at 8:42 AM, lee <lee at yun.yagibdah.de> wrote:

> Peter <peter at pajamian.dhs.org> writes:
> > On 06/12/2014 05:17 PM, lee wrote:
> >> I knew before I started that network setup would be a PITA because years
> >> ago, I set up a VM for someone who didn't have a 64bit system to compile
> >> a 64bit version of some software.  The network setup being so
> >> ridiculously difficult has kept me from touching VMs ever again for
> >> years.  It's just too difficult and not worth the effort unless you're
> >> really forced to do it.
> >
> > Networking can be confusing until it "clicks" then it all seems to fall
> > into place, there is a certain amount of understanding of the overall
> > picture of how bridge networking (or other types of networking) works
> > that once you get that understanding it becomes a lot simpler.
> I still don't really understand it.  For example, why does the dom0
> loose network connectivity when you add the physical interface through
> which it is connected to the network to a bridge?  The bridge supposedly
> connects networks indiscriminately, and it is illogical that the
> connection goes away when you connect a network to it.

Knowledge of what a network bridge would help you clarify that question. [2]
When you hook an interface to a Linux bridge the interface cannot be used
for anything else [0].  That is why IP addresses are instead placed on the
bridge interface [1].

I prefer to segregate management and VM physical interfaces.  One interface
is strictly used for managing the virtualization node and the other(s) are
for VMs.  Those others could be hooked to different Linux bridges (cabled
to your physical switch) or bonded together.  I do not have (nor need) IP
addresses on bridges with my set up.

You might find more in-depth explanations online, but this is what I
fielded quickly.

[1] http://xmodulo.com/2013/04/how-to-configure-linux-bridge-interface.html
[2] http://iomem.com/archives/4-Ethernet-Bridges-under-Linux.html

//  SilverTip257  //
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