Re: [Xen-users] Routed Network with Xen

[Simon Hobson <linux@xxxxxxxxxxxxxxxx>]

DN Singh wrote:

> Secondly (and I think, a lot easier), you should be able to do it 
> very simply with a "two interface" setup.
> Configure your Dom0 with one ordinary interface connected to your 
> ISP's service. This will have the IP 1.1.1.5 and it **NOT** 
> connected to a bridge.
> Create a bridge, but do not add a physical NIC to it (unless you 
> need other internal machines to have access). Give this an IP 
> address of 1.1.2.1/28.
> Now give your DomUs IPs in the rest of the 1.1.2.0/28 subnet (ie 
> 1.1.2.2 through 1.1.2.14), connect their VIF to the bridge defined 
> in the step above, and have them use 1.1.2.1 as their default 
> gateway.

> Also, you suggested binding the additional IPs to DomUs, which I had 
> tried, but the DomUs never got connected to the internet, as they 
> did not find any gateway. The DC suggests binding the IPs straight 
> away on the parent node, and they will get the gateway automatically 
> due to their statically bound nature. 
> <http://wiki.hetzner.de/index.php/Zusaetzliche_IP-Adressen/en>Refer 
> this link, as I feel I may be missing something from the it.
Then I suggest you go back and read what I wrote :-/ They don't 
"find" a gateway, you tell them what the gateway is - it's the 
"internal" side of the Dom0 routing.
Ie, showing just one DomU, you'd have :

ISP -- 1.1.1.5 eth0 - Dom0 - br0 1.1.2.1 -- vifx.y -- 1.1.2.2 eth0 - DomU

DomU needs only 3 bits of information, it's IP address, netmask, and 
default router. The latter is 1.1.2.1, the IP address in the inside 
of Dom0

> I think there is some confusion regarding the gateway, as the setup 
> seems to be getting complicated.
It shouldn't be, this is possibly one of the simplest possible 
configurations to set up !
From the above link, see this section :

> Problems with virtualization
> With this type of IP/subnet allocation, it is not possible to use a 
> "bridged" setup, as with such a setup several MAC addresses appear. 
> VPS (linux virtual servers, Xen, vmware, etc) must use a so-called 
> "Routed" setup (VMware: "host-only networking"). With an additional 
> subnet the host system or dom0 must be configured with an IP address 
> from the subnet which is then used as a gateway for the VPS. The 
> (additional) address of the host system must be configured in the 
> VPS in each case as a gateway.
It describes EXACTLY what I wrote above.

--
Simon Hobson

Visit http://www.magpiesnestpublishing.co.uk/ for books by acclaimed
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