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

["Dan Parsons" <dparsons@xxxxxxxx>]

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?

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

Thanks
Dan Parsons  

-----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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