Hello Simon

Thank you for the explanation, I greatly appreciate that.

Concerning the issue with kernel 2.6.20 and above, do you know the
restrictions or is it written somewhere?

On 02/08/07 14:08, "Simon Hobson" <[EMAIL PROTECTED]> wrote:

> Lars E. D. Jensen wrote:
> 
>> I have a couple of questions about http://www.shorewall.net/XenMyWay.html
>> 
>> 1. Why is the approach described not working with and above kernels 2.6.20?
>> What is not working?
> 
> The netfilter team made some changes to the way that physdev matching
> in a bridged environment works to cater for certain other
> configurations. With SHorewall v4 and the perl compiler it does work
> with some restrictions.
> 
>> 2. Is the configuration of Dom0 with two bridges a "shortcut" for the
>> traffic? That is if the following is valid this would not be necessary (Dom0
>> has 2 interfaces eth0 and eth1?
>> 
>> Phys.switch<----->Dom0-peth0<->Dom0-eth0<->xenbr0<->DomU-eth0-192.168.1.10
>> ^                                            (  | shortcut  )
>> |---------------->Dom0-peth1<->Dom0-eth1<->xenbr1<->DomU-eth1-192.168.1.20
>> 
>> I guess the shortcut wouldn't be a bad idea, but I would like to avoid
>> configuration of shorewall in Dom0 since Dom0 isn't used for anything.
> 
> Not sure what you mean here. There should be no way for packets to
> get between xenbr0 and xenbr1 without being passed by 'something' -
> where 'something' is software running on a domain with connections to
> both bridges. But your diagram is wrong anyway, traffic doesn't flow
> through dom-0 between a physical interface and the bridge - at least
> not in the conventional networking view, although pethn and xenbrn do
> appear in dom-0 as they have to 'exist' somewhere.
> 
> What you actually have, logical view, is :
> 
> Phys.switch0<----->peth0<->xenbr0<-+->Dom0-eth0
>                                     +->DomU-eth0-192.168.1.10
> 
> Phys.switch1<----->peth1<->xenbr1<-+->Dom0-eth1
>                                     +->DomU-eth1-192.168.1.20
> 
> Notice how there is no direct connection between the two 'networks'.
> I would not advise plugging both physical network ports into the same
> switch - that rather defeats the point of having a two-bridge setup
> and may create you a network loop (which believe me, you do NOT want
> unless you also use STP to disable some of the links). Phys.switch0
> might be your internet connection, and Phys.switch1 your internal
> network.
> 
> 
> Assuming that you have two separate networks, then you could run
> shorewall in bridging mode on dom-0, or in bridging or routing mode
> in dom-u. That changes your network to (using a bridge in dom-u):
> 
> Phys.switch0<----->peth0<->xenbr0<-+->Dom0-eth0
>                                     +->DomU-eth0-192.168.1.10<-+
>                                                               <br0>
> Phys.switch1<----->peth1<->xenbr1<-+->Dom0-eth1               |
>                                     +->DomU-eth1-192.168.1.20<-+
> 
> here, br0 is built inside domu and is not visible to anything else.
> 
> 
> Adding some more devices might get you to :
> 
> Phys.switch0<----->peth0<->xenbr0<-+->Dom0-eth0
>                                     +->Dom1-eth0-192.168.1.10<-+
>                                                               <br0>
> Phys.switch1<----->peth1<->xenbr1<-+->Dom0-eth1               |
>     ^ ^                             +->Dom1-eth1-192.168.1.20<-+
>     | |                             +->Dom2-eth0-192.168.1.21
>     | +->PC1                        +->Dom3-eth0-192.168.1.22
>     |
>     +-> PC2
> 
> 
> Or a slightly more real world :
> 
> DSl Modem<-------->peth0<->xenbr0<-+->Dom0-eth0
>                                     +->Dom1-eth0-a.b.c.d<------+
>                                                           <Route/NAT>
> Phys.switch1<----->peth1<->xenbr1<-+->Dom0-eth1-192.168.1.1   |
>     ^ ^                             +->Dom1-eth1-192.168.1.20<-+
>     | |                             +->Dom2-eth0-192.168.1.21
>     | +->PC1                        +->Dom3-eth0-192.168.1.22
>     |
>     +-> PC2
> 
> Where you see that only dom-1 has a public address, and although the
> packets do flow 'through' dom-0, dom-0 doesn't have any interface
> actually configured with an IP address outside of the firewall in
> dom1 and so 'should' be fairly safe.
> 
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-- 
Med venlig hilsen / Best regards
Lars E. D. Jensen
DCmedia Hosting, TYPO3 Development Partner
Dronningensgade 23, DK-5000 Odense C
Website: http://dcmediahosting.com
E-mail: [EMAIL PROTECTED]
Tlf.: +45 8888 7899
Direkte tlf.: +45 8888 7890


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