Xen users - Oct 2008 - Add independent interface from domU to internal bridge?

Hi,

I have what I believe is an elementary problem, but I haven''t yet 
figured out the solution.

Within my domU host, I have a bridge named "net1". There is no routing
performed between the real LAN and this bridge, intentionally. I have a 
virtual machine that connects to the bridge. It seems to work fine, (in 
fact I have several and I can bring them all up and they can communicate 
with each without incident).

My domU host has a single physical network interface which sits on my 
LAN and provides internet access for the domU host only (so I can send 
email, browse the web, etc, from domU).

What I don''t understand is how to do is to add another, uh, virtual NIC
that connects my domU host to the "net1" bridge that runs within it
but
that does not require connecting the LAN and the "net1" virtual
bridge.
Nearly all the documentation I have read is written from the point of 
view where the virtual network will be routed to the LAN via domU. It 
always just works with the built-in scripts, everyone''s happy. If I 
recall correctly, my implementation worked like this in the beginning, 
but ultimately in my case this is undesirable so I created my own 
bridges and altered the guest systems to utilize those. I deleted the 
bridges created by the xen scripts/distributions and disabled the built 
in DHCP/DNS server some time ago, because I want this to come from a 
virtual machine on the net1 bridge. DomU''s role is to provide a virtual
world to run in only, not services to the guest systems.
Other documents I''ve read suggest that I can achieve domU connectivity 
to the "net1" bridge by adding either the physical NIC or an alias of 
the physical NIC to the "net1" bridge using brctl. Anytime I
manipulate
the physical NIC in domU I lose LAN connectivity which is unacceptable.
I have tried enabling the dummy ethernet module via modprobe facilities 
but it seems to have no effect, or I don''t know how to interact with
it.
(It''s been a while since I worked this angle and I don''t
recall what I did.)
In at least one other document it seems that I could use `ip'' to
replace
the dummy ethernet module using ip but it ultimately required an 
ethernet device. That seems to be precisely my problem, I don''t have an
ethernet device in this machine that isn''t already busy doing
something.
Is that the answer? Must I have a separate physical ethernet device for 
every internal bridge that I want to connect to?

Trying to Google this problem is almost as frustrating as the problem. 
My attempts to search invariably match documentation for common setups 
which I don''t appear to have.
For what it''s worth, I''m running Fedora Core 8/Xen 3;
2.6.21-2950.fc8xen
(supplied via the Fedora distribution)
Any direction that might help me resolve this problem is greatly 
appreciated.

Thanks,
Rich.

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On Sat, Oct 4, 2008 at 1:55 PM, Xenu13542 <xenu@foxengines.net>
wrote:
> Hi,
>
> I have what I believe is an elementary problem, but I haven''t yet
figured
> out the solution.
>
> Within my domU host, I have a bridge named "net1". There is no
routing
> performed between the real LAN and this bridge, intentionally. I have a
> virtual machine that connects to the bridge. It seems to work fine, (in
fact
> I have several and I can bring them all up and they can communicate with
> each without incident).
>
> My domU host has a single physical network interface which sits on my LAN
> and provides internet access for the domU host only (so I can send email,
> browse the web, etc, from domU).
>
> What I don''t understand is how to do is to add another, uh,
virtual NIC that
> connects my domU host to the "net1" bridge that runs within it
but that does
> not require connecting the LAN and the "net1" virtual bridge.
> Nearly all the documentation I have read is written from the point of view
> where the virtual network will be routed to the LAN via domU. It always
just
> works with the built-in scripts, everyone''s happy. If I recall
correctly, my
> implementation worked like this in the beginning, but ultimately in my case
> this is undesirable so I created my own bridges and altered the guest
> systems to utilize those. I deleted the bridges created by the xen
> scripts/distributions and disabled the built in DHCP/DNS server some time
> ago, because I want this to come from a virtual machine on the net1 bridge.
> DomU''s role is to provide a virtual world to run in only, not
services to
> the guest systems.
> Other documents I''ve read suggest that I can achieve domU
connectivity to
> the "net1" bridge by adding either the physical NIC or an alias
of the
> physical NIC to the "net1" bridge using brctl. Anytime I
manipulate the
> physical NIC in domU I lose LAN connectivity which is unacceptable.
> I have tried enabling the dummy ethernet module via modprobe facilities but
> it seems to have no effect, or I don''t know how to interact with
it. (It''s
> been a while since I worked this angle and I don''t recall what I
did.)
> In at least one other document it seems that I could use `ip'' to
replace the
> dummy ethernet module using ip but it ultimately required an ethernet
> device. That seems to be precisely my problem, I don''t have an
ethernet
> device in this machine that isn''t already busy doing something. Is
that the
> answer? Must I have a separate physical ethernet device for every internal
> bridge that I want to connect to?
>
> Trying to Google this problem is almost as frustrating as the problem. My
> attempts to search invariably match documentation for common setups which I
> don''t appear to have.
> For what it''s worth, I''m running Fedora Core 8/Xen 3;
2.6.21-2950.fc8xen
> (supplied via the Fedora distribution)
> Any direction that might help me resolve this problem is greatly
> appreciated.
>
You can use a dummy device in dom0 as a bridge and give it to the guest
without having a physical device associated with it.

http://www.debian-administration.org/articles/360
http://wiki.xensource.com/xenwiki/XenNetworking
http://runningxen.com/resources/#chapter10

Cheers,
Todd

-- 
Todd Deshane
http://todddeshane.net
check out our book: http://runningxen.com

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>
> .
>
> Within my domU host,

DomU host?

-- 
Grant McWilliams

Some people, when confronted with a problem, think "I know, I''ll
use
Windows."
Now they have two problems.


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This makes sense to me… any OS instance is a host.
 
Thank you,
Nathan Eisenberg
Sr. Systems Administrator
Atlas Networks, LLC.
 
From: xen-users-bounces@lists.xensource.com
[mailto:xen-users-bounces@lists.xensource.com] On Behalf Of Grant McWilliams
Sent: Sunday, October 05, 2008 9:49 AM
To: Xenu13542
Cc: Xen-Users
Subject: Re: [Xen-users] Add independent interface from domU to internal bridge?
 
.

Within my domU host,

DomU host?

-- 
Grant McWilliams

Some people, when confronted with a problem, think "I know, I''ll
use Windows."
Now they have two problems.

_______________________________________________
Xen-users mailing list
Xen-users@lists.xensource.com
http://lists.xensource.com/xen-users

On Sun, Oct 5, 2008 at 10:01 AM, Nathan Eisenberg
<nathan@atlasnetworks.us>wrote:
>  This makes sense to me… any OS instance is a host.
>
>
>
> Thank you,
>
> Nathan Eisenberg
>
> Sr. Systems Administrator
>
> Atlas Networks, LLC.
>
>
>
Maybe if you're talking networks... That term gets used in too many
different ways, like the domain word.

-- 
Grant McWilliams

Some people, when confronted with a problem, think "I know, I'll use
Windows."
Now they have two problems.


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Xen-users mailing list
Xen-users@lists.xensource.com
http://lists.xensource.com/xen-users