[Fedora-xen] Multihomed networking

Ben bench at silentmedia.com
Tue Apr 25 02:03:55 UTC 2006


Yes, but not with the default xen bridging scripts.

On Apr 24, 2006, at 6:27 PM, Mark A Heilpern wrote:

> Is anyone using FC5 Xen with an FC5 guest, where the Dom0 has two  
> ethernet devices (succesfully)?
>
> My system has eth0 as a 192.168.2.x network, eth1 as my static  
> Internet address, and iptables NAT between them. All real machines  
> on my home network can get out just fine.
>
> My guest VM, also a 192.168.2.x address, is able to reach other  
> machines on my internal network without problem, but trying to  
> access the internet doesn't work. At first I thought it was an  
> iptables configuration issue on the Dom0 machine, but I don't think  
> so anymore. As a test, I inserted at the top of every table a rule  
> to emit a log message when any machine on my net tried to access a  
> specific remote host; performing a wget command in the guest VM  
> shows my outbound SYN, shows an incoming SYN+ACK from the remote  
> host (so outbound masquarading must be working?) and an outbound  
> ACK (so incoming demasquarading must be working?)... I never  
> receive another packet from the remote host (until quite a while  
> later, when I receive FIN). If I try the same exercise with a real  
> host on my network, I get a normal data stream in/out.
>
> Also, traceroute from the guest VM doesn't work exactly as I would  
> expect. I would expect the results of one to be quite similar to  
> those from my Dom0 machine, but consistantly I am missing responses  
> along the path. For example:
>
>
>> From dom0:
> [root at heilpern ~]# traceroute www.yahoo.com
> traceroute to www.yahoo.com (216.109.117.106), 30 hops max, 40 byte  
> packets
>  1  [my cable modem]
>  2  10.106.32.1 (10.106.32.1)  8.279 ms   11.786 ms *
>  3  * * *
>  4  * * *
>  5  * * *
>  6  * * *
>  7  ae-0-0.bbr2.Washington1.Level3.net (4.68.128.210)  45.855 ms * *
>  8  ae-21-54.car1.Washington1.Level3.net (4.68.121.114)  35.593 ms  
> ae-21-56.car1.Washington1.Level3.net (4.68.121.178)  35.382 ms    
> 41.539 ms
>  9  4.79.228.2 (4.79.228.2)  40.073 ms   39.931 ms *
> 10  * * *
> 11  * * *
> 12  * p21.www.dcn.yahoo.com (216.109.117.106)  35.227 ms *
>
>
>> From the guest VM:
> [root at testvm ~]# traceroute www.yahoo.com
> traceroute to www.yahoo.com (216.109.117.106), 30 hops max, 40 byte  
> packets
>  1  192.168.2.1 (192.168.2.1)  0.000 ms   0.000 ms   0.000 ms
>  2  [my cable modem]
>  3  10.106.32.1 (10.106.32.1)  9.910 ms   13.919 ms *
>  4  * * *
>  5  * * *
>  6  * * *
>  7  * * *
>  8  ae-0-0.bbr2.Washington1.Level3.net (4.68.128.210)  48.307 ms * *
>  9  ae-11-51.car1.Washington1.Level3.net (4.68.121.18)  37.938 ms    
> 42.377 ms ae-21-54.car1.Washington1.Level3.net (4.68.121.114)   
> 43.048 ms
> 10  4.79.228.2 (4.79.228.2)  45.568 ms   43.918 ms *
> 11  * * *
> 12  * * *
> 13  * * *
> 14  * * *
> 15  * * *
> 16  * * *
> 17  * * *
> 18  * * *
> 19  * * *
> 20  * * *
> 21  * * *
> 22  * * *
> 23  * * *
> 24  * * *
> 25  * * *
> 26  * * *
> 27  * * *
> 28  * * *
> 29  * * *
> 30  * * *
> [root at testvm ~]#
>
>
>
> This is pretty repeatable.
>
> Any thoughts?
>
>
> Here are my Dom0 configurations:
> [root at heilpern ~]# brctl show
> bridge name     bridge id               STP enabled     interfaces
> xenbr0          8000.feffffffffff       no              peth0
>                                                         vif0.0
>                                                         vif2.0
> [root at heilpern ~]# ifconfig eth0
> eth0      Link encap:Ethernet  HWaddr 00:10:DC:F2:70:17
>           inet addr:192.168.2.1  Bcast:192.168.2.255  Mask: 
> 255.255.255.0
>           inet6 addr: fe80::210:dcff:fef2:7017/64 Scope:Link
>           UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
>           RX packets:733780 errors:0 dropped:0 overruns:0 frame:0
>           TX packets:822036 errors:0 dropped:0 overruns:0 carrier:0
>           collisions:0 txqueuelen:0
>           RX bytes:87799449 (83.7 MiB)  TX bytes:207088442 (197.4 MiB)
>
> [root at heilpern ~]# ifconfig eth1
> eth1      Link encap:Ethernet  HWaddr 00:90:47:03:B8:63
>           inet addr:[my IP]  Bcast:[my BCAST IP]  Mask:255.255.255.252
>           inet6 addr: fe80::290:47ff:fe03:b863/64 Scope:Link
>           UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
>           RX packets:829216 errors:0 dropped:0 overruns:0 frame:0
>           TX packets:556902 errors:0 dropped:0 overruns:0 carrier:0
>           collisions:0 txqueuelen:1000
>           RX bytes:169446616 (161.5 MiB)  TX bytes:85050877 (81.1 MiB)
>           Interrupt:18
>
> [root at heilpern ~]# iptables -t nat -L
> Chain PREROUTING (policy ACCEPT)
> target     prot opt source               destination
>
> Chain POSTROUTING (policy ACCEPT)
> target     prot opt source               destination
> MASQUERADE  all  --  anywhere             anywhere
>
> Chain OUTPUT (policy ACCEPT)
> target     prot opt source               destination
>
> (temporary wide-open rules):
> [root at heilpern ~]# iptables -L
> Chain INPUT (policy ACCEPT)
> target     prot opt source               destination
>
> Chain FORWARD (policy ACCEPT)
> target     prot opt source               destination
>
> Chain OUTPUT (policy ACCEPT)
> target     prot opt source               destination
>
> Chain INBOUND (0 references)
> target     prot opt source               destination
>
> Chain LOG_FILTER (0 references)
> target     prot opt source               destination
>
> Chain LSI (0 references)
> target     prot opt source               destination
>
> Chain LSO (0 references)
> target     prot opt source               destination
>
> Chain OUTBOUND (0 references)
> target     prot opt source               destination
>
>
>
> Thanks in advance...
> Mark
>
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