How is network bridging for Xen handled in F7?

[Christian Reiter]

Hi!


Can anybody tell me where i can find docs about handling network bridges for xen domUs in
Fedora 7?

Something changed since FC6, so i cannot figure out how to create simple bridges without
dhcp for my xen domUs.

All what i want is:
xenbrINTERNET should bridge to eth1
xenbrLAN      should bridge to eth0

eth0 and eth1 of my dom0 should also have an IP Address.
I do not want routing or nat for my domUs.


Thanks!

regards,
christian

[Daniel P. Berrange]

On Tue, Jun 05, 2007 at 06:58:31PM +0200, Christian Reiter wrote:
>  Hi!
>  
>  
>  Can anybody tell me where i can find docs about handling network bridges for xen domUs in
> Fedora 7?
>  
>  Something changed since FC6, so i cannot figure out how to create simple bridges without
> dhcp for my xen domUs. 
Previously there was a xen module called 'netloop' in use. So if you used
network-bridge, you'd get 4 interfaces

  peth0    - physical device
  xenbr0   - bridge device
  vif0.0   - backend of virtual device
  eth0     - frontend of virtual device

peth0 & vif0.0 would be part of xenbr0


In F7, use of netloop is removed to simplify dom0 config so you only get
two interfaces

  peth0  - physical device
  eth0   - bridge device

And peth0 is part of the eth0 bridge.

In both cases, eth0 wouldbe the device that gets the IP addr.

>  All what i want is:
>  xenbrINTERNET should bridge to eth1
>  xenbrLAN      should bridge to eth0 
Calling the bridge xenbrXXXX is deprecated, since we're moving towards a Dom0
config which is able to be the same for both Xen and KVM. Hence we have the
generic peth0 & eth0  devices now. That's a minor naming detail though. You
should be able to call network-bridge multiple times - once per device you
have, just as with Fc6. Alternatively setup briding using the regular init
scripts as per section 2 in this doc

http://watzmann.net/blog/index.php/2007/04/27/networking_with_kvm_and_lib...

Dan.
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[Daniel P. Berrange]

On Tue, Jun 05, 2007 at 06:23:57PM +0100, Daniel P. Berrange wrote:
>  On Tue, Jun 05, 2007 at 06:58:31PM +0200, Christian Reiter wrote:
>  > Hi!
>  > 
>  > 
>  > Can anybody tell me where i can find docs about handling network bridges for xen
> domUs in Fedora 7?
>  > 
>  > Something changed since FC6, so i cannot figure out how to create simple bridges
> without dhcp for my xen domUs.
>  
>  Previously there was a xen module called 'netloop' in use. So if you used
>  network-bridge, you'd get 4 interfaces
>  
>    peth0    - physical device
>    xenbr0   - bridge device
>    vif0.0   - backend of virtual device
>    eth0     - frontend of virtual device
>  
>  peth0 & vif0.0 would be part of xenbr0
>  
>  
>  In F7, use of netloop is removed to simplify dom0 config so you only get
>  two interfaces
>  
>    peth0  - physical device
>    eth0   - bridge device
>  
>  And peth0 is part of the eth0 bridge. 

Oh btw, before anyone asks - we added compatability code to vif-bridge, so if
you have any existing guest config files which refer to 'xenbr0' they will
automatically join the eth0 bridge device instead. So existing guests are 
supposed to 'just work' even though the Dom0 network config changed a little.

Dan.
-- 
|=- Red Hat, Engineering, Emerging Technologies, Boston.  [phone] -=|
|=-           Perl modules: http://search.cpan.org/~danberr/              -=|
|=-               Projects: http://freshmeat.net/~danielpb/               -=|
|=-  GnuPG: 7D3B9505   F3C9 553F A1DA 4AC2 5648 23C1 B3DF F742 7D3B 9505  -=|

[Christian Reiter]

Thanks Daniel, that worked perfect!

One further Question:
Is there any way to get rid of the virbr0 Interface?
I've already deleted in the virt-manager GUI.

chris


Mit freundlichen Grüßen,  ///  Kind Regards,
                                                 Christian Reiter



-- 

Christian Reiter	|||	c.reiter(a)gmx.net

[Daniel P. Berrange]

On Wed, Jun 06, 2007 at 06:27:24PM +0200, Christian Reiter wrote:
>  Thanks Daniel, that worked perfect!
>  
>  One further Question:
>  Is there any way to get rid of the virbr0 Interface? 
This is the libvirt provided virtual network, connected using NAT, so
you can use the virt-manager UI to stop/start the network. Or from
the command line you can:

  virsh net-destroy default

And to make that permanent

  virsh net-autostart --disable default

Dan.
-- 
|=- Red Hat, Engineering, Emerging Technologies, Boston.  [phone] -=|
|=-           Perl modules: http://search.cpan.org/~danberr/              -=|
|=-               Projects: http://freshmeat.net/~danielpb/               -=|
|=-  GnuPG: 7D3B9505   F3C9 553F A1DA 4AC2 5648 23C1 B3DF F742 7D3B 9505  -=|

[Robin Bowes]

Daniel P. Berrange wrote:

>  Oh btw, before anyone asks - we added compatability code to
> vif-bridge, so if
>  you have any existing guest config files which refer to 'xenbr0' they will
>  automatically join the eth0 bridge device instead. So existing guests are 
>  supposed to 'just work' even though the Dom0 network config changed a little.
Dan,

I just ran into an issue with this.

I have re-built F8 xen-3.1.2 from SRPM on CentOS 5.1 x86_64 and done a 
clean kickstart install of CentOS 5.1 x86_64 which pulls in the 
xen-3.1.2 RPMs from a repo (i.e. xen-3.0.3 is never installed).

I have some guests created using xen-??? on FC6 which I have migrated to 
a new machine and which use xenbr0.

When I try to start the domains using "xm create -c guestname" I got a 
message about not finding xenbr0.

So, I changed xenvr0 to virbr0 and the guests start OK and can talk to 
each other but can not talk to anything on the rest of the network.

I have figured that this is related to the issue discussed in this thread.

How come xenbr0 was not recognised? Do I need to update some other 
packages, or should I use virsh?

Or do I just configure eth0 as a bridge in Dom0 as described here [1]

Thanks,

R.

[1] 
http://watzmann.net/blog/index.php/2007/04/27/networking_with_kvm_and_lib...

[Robin Bowes]

Robin Bowes wrote:

>  How come xenbr0 was not recognised? Do I need to update some other 
>  packages, or should I use virsh? 
OK, I've answered my own question.

I've rebuilt the following packages from Fedora 8 on CentOS 5.1 x86_64, 
added them to my own yum repo, then done a clean kickstart install of 
CentOS 5.1 using my yum repo as a source.

The result? It all seems to be working very nicely! The networking on my 
old domains (that use xenbr0 in the config files) work without any 
modification.

These are the packages I re-built:

	libvirt-0.4.0-4
	virt-viewer-0.0.2-2
	xen-libs-3.1.2-1
	gtk-vnc-0.2.0-4
	libvirt-python-0.4.0-4
	python-virtinst-0.300.2-2
	xen-3.1.2-1.x86_64

The binaries are in my repo here:

	http://repo.yo61.net/

Specifically, here:

	http://repo.yo61.net/centos/5/x86_64/RPMS/

Hopefully, this will keep me going for a while!

R.

[Christian Reiter]

Thanks Dan!

I'll try as soon as i'm back in the Office and report here.

christian