Re: [Xen-users] routed networking

[Michael Froh <michael.froh@xxxxxxxxxx>]

On 27-Nov-06, at 4:11 PM, Pete McEvoy wrote:

> On Mon, Nov 27, 2006 at 03:46:36PM -0500, Michael Froh wrote:
> >    I am also new to xen so take with a grain of salt.  I found the  
> > networking
> >    wiki
> >    page to be very useful in understanding how xen networking  
> > functions:
> >    http://wiki.xensource.com/xenwiki/XenNetworking
> >    My interpretation of your requirements and this wiki page are:
> >    - you want all DomU's visible to Internet
> >    - you want DomU to have a single eth interface
> >    - you want to use bridge networking
> >    - you don't mind having Dom0 publicly addressable
> >    - xenbr0 (bridge) does not use an IP (as per wiki)
> >    Then you should need an IP address for each of the eth  
> > interfaces on your
> >    physical server and one for each of your DomU vms.  For example  
> > if your
> >    server has a single eth0 interface, you would need 3 IPs for  
> > each of Dom0,
> >    DomU1 and DomU2.
> Thanks for replying.
> That pretty much sums it up, so am I to assume its as simple as
> changing the line I use from (vif-script vif-bridge) to (vif-script
> vif-route) in xend-config.sxp and configuring my dom0 and domUs in a
> 'normal' manner with the 3 ips I'm provided?
>
> If so, I feel pretty stupid..
>
> Thanks again.
>
> --
> Pete
I don't think you have to move to the routed xen configuration (I do not
have any experience yet).  I do know that on my bridged xen machine I
can run many vms, all with unique mac addresses and dhcp issued IPs.
I can arp/ping between any real host and any virtual machine.

The only reason I would see for running the routed xen networking is if
there are other xen vms running in bridge mode and there is a MAC
address collision on the ISPs LAN.  That is, a collision in the IEEE
assigned xen MAC address space (00:16:3e:xx:xx:xx).  Assuming xen
actually assigns MAC addresses randomly, then the chance of a collision
is still pretty small given there are over 16 million unique xen MAC
addresses.  I suppose this would be a reason to have xen randomly
assign MACs in an ISP setting to reduce the chance of MAC collision.
To do this you just include the "vif = [ '' ]" line in your vm config.

Assuming your ISP is giving you static IPs, you would just bring up eth0
in your vm using normal methods for our linux using the ISP assigned
static IP.

Mike.

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