Re: [Xen-users] NET Network / Server running on internal Network not reachable

[Robert M. Münch <robert.muench@xxxxxxxxxxxxxxx>]

On Tue, 08 Jul 2008 21:05:05 +0200, Robert M. Münch  
<robert.muench@xxxxxxxxxxxxxxx> wrote:
> Hi all, since several days I try to get NAT networking to work, which is  
> driving my nuts... I don't know what to do anymore. Maybe some expert  
> have a good tip for me. I have ready almost anything about this topic  
> and tested most stuff, but still no luck.
> I want to run a web-server on a DomU. Hence I used the normal NAT setup  
>  from xen.
> Current setup & situation
>
> 1. DomO can access the internet
> 2. Dom0 can access the DomU
> 3. DomU (10.0.0.1) can access the internet
> 4. DomU can access Dom0
>
> What's not working is that I can't reach the web-server running on DomU.
Hi, answering to my own posting, I have found out something I think is the  
source of the problem:
> Chain PREROUTING (policy ACCEPT)
> target     prot opt source               destination
> DNAT       tcp  --  anywhere             eisxen              tcp dpt:www  
> to:10.0.0.1:80
This rule should rewrite the incoming TCP packet with a new internal IP,  
so that the normal routing than routes it to the VM running the web-server.
But TCPDUMP shows that the packet goes into PREROUTING and than into  
FORWARD:
PREROUTING ENTER: IN=xenbr0 OUT= PHYSIN=peth0  
MAC=00:11:6b:94:d8:ea:00:18:74:84:8c:00:08:00 SRC=153.57.18.221  
DST=87.118.120.16 LEN=48 TOS=0x00 PREC=0x00 TTL=57 ID=54899 DF PROTO=TCP  
SPT=63149 DPT=80 WINDOW=64240 RES=0x00 SYN URGP=0
FORWARD ENTER: IN=xenbr0 OUT=xenbr0 PHYSIN=peth0 PHYSOUT=vif0.0  
SRC=153.57.18.221 DST=87.118.120.16 LEN=40 TOS=0x00 PREC=0x00 TTL=57  
ID=54898 DF PROTO=TCP SPT=37545 DPT=80 WINDOW=64240 RES=0x00 RST URGP=0
And DST=87.118.120.16 is my external static IP. I expected here  
DST=10.0.0.1
Than I have this error message: Performing cross-bridge DNAT requires IP  
forwarding to be enabled
I have searched for this but didn't found anything useful. Routing is  
enabled but I still think there are some problems. I'm not sure if this is  
the source of the problem that the IP isn't rewritten.
Is this a known problem? Does anyone know a solution to this?

--
Robert M. Münch
http://www.robertmuench.de

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