Subject: Re: [vserver] strange networking behaviour
From: Herbert Poetzl <herbert@13thfloor.at>
Date: Tue, 6 Sep 2011 11:48:03 +0200

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