Re: [Xen-users] what the H is this virbr0?

[Sadique Puthen <sputhenp@xxxxxxxxxx>]

Steven wrote:
> Sadique Puthen wrote:
> > Steven wrote:
> > > Hi,
> > >
> > > I just tested in the lab the new CentOS 5.1 Xen and find out it 
> > > breaks network connectivity, at least in my setup.
> > > It seems it is somehow making use of the 3.1 Xen version (altought I 
> > > am not sure about that) but whatever changes it introduce is not 
> > > documented at the location one would expect, the obvious new thing 
> > > (at least for me) is this thing I will call out of guessing a 
> > > virtual bridge, when I do an ifconfig on the dom0:
> > > virbr0    Link encap:Ethernet  HWaddr FE:FF:FF:FF:FF:FF
> > >          inet addr:192.168.122.1  Bcast:192.168.122.255
> > > This seems to change everything with regard to networking. I 
> > > googgled a bit and read the following links but I could not find any 
> > > explanation about what it is, what it does and why it breaks my setup:
> > Centos 5.1 makes networking for guests a bit easier by adding virb0 
> > and implementing a natted network connection for guests. This 
> > shouldn't break the networking that you had previously in Centos-5.0. 
> > At least it has not broken anything on my RHEL5 system when I 
> > upgraded that to RHEL-5.1
> > RHEL-5.1 makes it possible for you to put guests in a private network 
> > behind dom0 and nat packets to your LAN through dom0. This is the 
> > preferred set up for laptops. If you create guests using 
> > virt-manager, it defaults the network setup to use natting, unless 
> > you explicitly select to bridge the network to xenbrx. The problem is 
> > that RHEL-5.1 does not enable ip forwarding by default in the kernel. 
> > So if you create guests and bridge them to virbr0, the guest wouldn't 
> > be able to communicate to the external networks. This can simply be 
> > solved by enabling ip forwarding in Dom0.
> Ok, thank you. Do you know how or where to disable it?
/etc/libvirt/qemu/networks/autostart/default.xml

--Sadique

> > --Sadique
> >
> > > http://wiki.xensource.com/xenwiki/XenNetworking
> > > http://www.cl.cam.ac.uk/research/srg/netos/xen/readmes/user/user.html#SECTION03220000000000000000 
> > >
> > > Can anyone point to an official information source for this beast?
> > >
> > > Regards,
> >
> > _______________________________________________
> > Xen-users mailing list
> > Xen-users@xxxxxxxxxxxxxxxxxxx
> > http://lists.xensource.com/xen-users

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