Re: [Xen-users] Bridging with multiple public IPs

["Fajar A. Nugraha" <fajar@xxxxxxxxx>]

On Fri, Mar 27, 2009 at 2:46 PM, Ravikesh Chandra
<rcha108@xxxxxxxxxxxxxxxxx> wrote:
>> > Firstly my Dom0 has a IP (let's say) 75.59.43.140 with gateway
>> > 75.59.43.190
>> > given to me with the server.
>> > I have then been given (let's say) 75.59.18.150 and using same gateway
>> > 75.59.43.190.
>>
>> Is this for real? Are you REALLY using a netmask of 255.255.0.0 (or
>> similar)?
>>
>
> Thanks for your reply. Well yes those are the IPs that I have been given...
> to be honest I'm not very well versed in networking so please tell me if
> they seem 'wrong' for instance I was surprised that I should use the same
> gateway?

Please keep list traffic on the list.
It's basic TCP/IP, actually. The host IP address and gateway should be
on the same network.
http://en.wikipedia.org/wiki/Classless_Inter-Domain_Routing
http://en.wikipedia.org/wiki/Subnetwork

>
> Anyway I have changed the bridge as you have suggested and now the output of
> "brctl show" seems correct:
> xenbr0        8000.feffffffffff    no        vif35.0
>                             peth0
>                             vif0.0
>
> So the DomU (vif35.0) is properly bridged with Dom0 (peth0, vif0.0) I

>From that output, yes. That is assuming your network guys put two
different IP networks on the same link (which is eth0 on your server)
without vlan or anything. Not recommended, but possible.

> assume? Unfortunately I still don't seem to have any network access from the
> DomU, here is the snippet from the Xen config file (with same settings in
> OS):
>
> vif = [ "ip=75.59.13.145,mac=00:16:3e:01:9d:36,bridge=xenbr0" ]
> netmask = "255.255.255.248"
> gateway = "75.59.43.190"

I prefer to have IP setup inside domU using the usual scripts. On
redhat it's /etc/sysconfig/network-scripts/ifcfg-eth0 (or similar).
That means on xen config file it's enough to put something like this

vif = [ "mac=00:16:3e:01:9d:36,bridge=xenbr0" ]

Your IP, netmask, and gateway combo is not right. They're not on the
same network.
Ask your network guys.

One way to easily test connectivity is to use an IP address in the
same network as dom0, and ping dom0 from domU. So (for example) if
dom0 has IP address 10.0.0.2/24, you can assign domU 10.0.0.3/24 and
ping dom0 from domU. Again, this is just an example. You should ask
your network guys to assign an IP address on the same network as your
dom0.

Regards,

Fajar

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