Subject: Re: [vserver] strange networking behaviour
From: Herbert Poetzl <herbert@13thfloor.at>
Date: Tue, 6 Sep 2011 13:17:19 +0200

On Tue, Sep 06, 2011 at 08:09:59PM +1000, Steve Kieu wrote:
> Thanks , the main thing I want to know is if I can use a bridge
> interface for a vserver guest.

yes, definitely, I'm using Linux-VServer and kvm side by side
on several systems and there is no problem whatsoever with
using a bridge for the guest IP(s)

> I do not think any of the problem coming from vserver code
> though - I would think of kernel bug somehow in the bridge code
> (does not actually disable STP ).

I don't think your problems are STP related, but I might be
wrong here (too little detail too many variables :)

in any case, I'd suggest to setup systems with everything
but one component removed and verify that it behaves as
expected (in the same setup used for the whole system)

e.g. remove the Linux-VServer patch, but setup the guest
IP(s) manually on the bridge and verify that they work
properly, on a second try, remove the proxmox part and
configure the bridge manually and see if you can use it
properly, and so on and so forth ...

> Once again thanks for your answer.

you're welcome!

best,
Herbert

> cheers

> On Tue, Sep 6, 2011 at 7:48 PM, Herbert Poetzl <herbert@13thfloor.at> wrote:

>> On Tue, Sep 06, 2011 at 02:02:49PM +1000, Steve Kieu wrote:

>>> Hello everyone,

>>> I am experiencing strange networking behavior not sure why.

>>> I ran a proxmox distro but (debian based on lenny) but using
>>> kernel 2.6.32.43-vs2.3.0.36.29.7. so just use proxmox to handle
>>> kvm and the rest is vserver.

>>> Proxmox created a bridge vmbr0 and bridge it with eth0 (main
>>> physical NIC connected to the LAN) - vmbr0 has an external IP
>>> 10.200.10.20/24. All kvm will use tap devices and bridge to
>>> vmbr0.

>>> Now I use vservers setup using vmbr0 as its interface - so that
>>> they can be the same network 10.200.10.0/24 - is it possible to
>>> use a bridge as an interface for a vserver guest?

>> the interface itself does not matter to Linux-VServer setups,
>> only the IP(s) assigned to the guest ...

>>> The strange thing here is, all IP in the vserver space does not
>>> visible from other host in the different network (not tested if
>>> the same network though) - Only OK if I do a

>>> arping -U -I vmbr0 IP

>>> and then Ctrl+C to stop it which is weird as just restarting
>>> the box, and I need to do it again - pretty sure the arp
>>> cache timeout of our router is 4 hours but it happened since
>>> yesterday afternoon till now, far more than that time.

>> well, Linux-VServer operates on the IP layer, so it doesn't
>> care about the interface setup or configuration, but of course
>> if your bridge is filtered or configured to prevent arp, then
>> the network environment will not know about any IP you add
>> (note: this is not Linux-VServer related at all, it is just
>> the host/interface config)

>>> Also if I stared new kvm or stop existing kvm, the host lose
>>> all network connectivity for several seconds and then the main
>>> IP (.20) recover by itself, but all other vserver IP is not,
>>> Need to run the arping again. <sigh>

>> sounds to me like there are some host scripts (proxmox stuff?)
>> doing the 'wrong' thing with the interface/bridge, you might
>> want to try without that (note: kvm doesn't need any special
>> configuration to work 'just fine')

>>> I do not know what I did wrong, maybe something obvious that I
>>> miss. The bridge , stp is disabled, and fd is set to 0 (proxmox
>>> set it automatically)

>>> any idea why it is doing that way? many thanks,

>> no idea why proxmox is doing that, but you better ask the
>> proxmox developers for that ...

>> HTH,
>> Herbert

>>> cheers
>>> -- Steve Kieu




> -- 
> Steve Kieu