Re: [Xen-users] Multiple IPs in a domU (I am using static macs)

[Tim Post <tim.post@xxxxxxxxxxxxxxx>]

On Mon, 2007-02-26 at 11:39 +0000, Dan Parsons wrote:
> Thanks for the suggestions. 
> Did something I say make you think I'm using a HVM? I'm using a plain old 
> paravirtualized VM here. 
> Does this change any of your suggestions?

No, not at all. I just suspected everything would be effected. There are
some known netdev quirks with hvm guests, was just pointing out to check
upstream before going after issues there too.

> My worry about the ping fix is that if there is no traffic on that IP for a 
> long time, 
> the arp record created by the ping will die. 
> And then the router issues another arp who-has, and we have the same problem. 
> Indeed, it looks as if Xen is ignoring who-has requests for eth1's IP.... 


> Also, how can it be upstream when the eth0 ip works just fine? It's just 
> eth1's ip that's bad.

THAT's where I mis read you. I thought this was on a bridge porting
eth0.


> What is xen doing to make eth0 work, that it's not doing for eth1? And why?

The magic is happening in /etc/xen/scripts/network-bridge , which is run
to construct the bridges when xen starts and take them down / restore
things when xen exits.

Within xend-config, you can pass paramaters to it. I personally don't
use it, I like to let my network init scripts handle the bridges because
I do more with bridging than Xen needs to do. 

> 
> Thanks
> Dan Parsons  
> 

Now it makes sense, and no , I don't think its upstream anymore. I'm
more dense than usual for some reason today.

Best,
--Tim

> -----Original Message-----
> From: Tim Post <tim.post@xxxxxxxxxxxxxxx>
> Date: Mon, 26 Feb 2007 19:30:21 
> To:dparsons@xxxxxxxx
> Subject: [QUAR] Re: [Xen-users] Multiple IPs in a domU (I am using static 
> macs)
> 
> On Mon, 2007-02-26 at 10:18 +0000, Dan Parsons wrote:
> > Thank you, but I actually am using statically defined  MACs in the domU 
> > config.. 
> > So I don't believe what you said applies. Please correct me if I'm wrong.
> 
> Ah no, you're right I had a brainfart. Mac was staring right at me in
> your config file. 
> 
> > Do you have further suggestions?
> 
> I haven't run into this, but only a few of my guests are HVM. You could
> try a couple of things.
> 
> If you are using Xen's network-bridge script to bring up your bridges,
> try letting init do it and use a network-dummy script in its place, play
> with the bridge settings and see if it helps.
> 
> forward delay, helo, maxwait, should be set to 0. I am not entirely sure
> that they are set to 0 by default by brctl.
>  
> Or a quick fix, call ping during the boot process on the guest slightly
> modifying the init strings until you can rule out exactly what the issue
> is.
> 
> I'm tending to lean in the direction of something upstream, though.
> 
> Best,
> --Tim
> 
> > Dan Parsons 
> > 
> > -----Original Message-----
> > From: Tim Post <tim.post@xxxxxxxxxxxxxxx>
> > Date: Mon, 26 Feb 2007 18:05:53 
> > To:Dan Parsons <dparsons@xxxxxxxx>
> > Cc:xen-users@xxxxxxxxxxxxxxxxxxx
> > Subject: [QUAR] Re: [Xen-users] Multiple IPs in a domU
> > 
> > On Sun, 2007-02-25 at 21:54 -0800, Dan Parsons wrote:
> > > I've been trying to make multiple public IP addresses work in a domU,  
> > > and have been unable to do it. I've tried every method mentioned in  
> > > the xenu-users archive as well as through a lot of stuff mentioned in  
> > > google.
> > 
> > >  Then the IP works. So,  
> > > it's a MAC/ARP issue.
> > 
> > Most cisco routers take up to ~9 minutes to re-arp these changes. Static
> > MACS must be used. 
> > 
> > You could tri arping'ing the gateway just specifying the address and
> > interface (i.e. eth0:1) or pass a -U. This should trick the router into
> > doing it.
> > 
> > The best way, use static macs when bringing up the vifs within the
> > dom-u. Remember, you can have only 3 physical eth devices within a
> > guest, as far as I know this limitation has not yet increased. 
> > 
> > So, its much easier to bring them up as vifs from within the dom-u
> > itself, just specify macs for each one. 
> > 
> > > But why isn't the MAC for eth1 being announced?
> > 
> > It is. apring is being called each time its brought to an up state to
> > make sure the IP does not already exist on the network. You either have
> > to wait 10 minutes, send traffic from it (i.e. ping -I eth0:1 -c1 -w5
> > 4.2.2.2 > /dev/null 2>&1 in the postup init script. It really depends on
> > the router.
> > 
> > > I've tried specifying  
> > > the IPs in the domU config various ways and that also didn't help.
> > 
> > That's not going to make much of a difference. I often just specify
> > bridge, vifname and mac and handle the rest inside of the guest.
> > 
> > > This is on Fedora Core 6, using Xen 3.0.3. domU is also FC6 using the  
> > > same kernel. kernel is 2.6.19-1.2911.fc6xen. Below is a bunch more  
> > > info, please tell me if I've forgotten to include anything.
> > 
> > Just flushing the router's arp hehehe :)
> > > 
> > > domU config file:
> > ,,, looked just fine to me.
> > > 
> > [ snip ]


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