Re: [Xen-devel] virbr0/bridge: No such file or directory, rhel6 bridge-utils IGMP snooping

[Pasi Kärkkäinen <pasik@xxxxxx>]

On Tue, Aug 30, 2011 at 09:59:03AM -0500, Scott Meyers wrote:
> 
> Pasi,
>  

I think we should move this thread to xen-users mailinglist..


> 
> > > > - do you have ip_forwarding (routing) enabled in dom0?
> > > 
> > > No. That was not mentioned or required according to your tutorial.
> > > 
> > 
> > NAT requires ip_forwarding/routing! This is a generic requirement for all 
> > Linux NAT stuff,
> > be it Xen or something else.
> 
> 
> I am using i686 arch system, NOT x86_64. Did you try your tutorial on a i686 
> system and worked? Were you able to add DomU successfully?
> 

Nope, I didn't try it on i686..


>  
> 
> Do you mind telling me how to set ip_forwarding? What file and what variable?
> 

It's shown in the http://wiki.xen.org/xenwiki/Fedora13Xen4Tutorial

echo 1 > /proc/sys/net/ipv4/ip_forward

or edit /etc/sysctl.conf and add it there..

>  
> 
>  
> 
>  
> 
> > > > - How are your firewall rules in dom0?
> > > 
> > > 
> > > Disabled
> > > 
> > 
> > Then it obviously won't work!
> > When dnsmasq starts it should add the firewall rules for NAT.
> 
> 
> I thought, SElinux must be disabled. In addition, I can not use DHCP in our 
> network. I am using ststic IPs.
> 


virbr0 is an internal bridge, it's only connected to dom0, so it's not visible 
to physical network.
You can freely use dhcp on virbr0.


>  
> 
>  
> 
>  
> 
> > > > - Is dnsmasq running?
> > > No, dsnmasq was not running. I started dnsmasq, but didn't solve the 
> > > problem.
> > > 
> > 
> > dnsmasq acts as a dhcp server and DNS server for virbr0 bridge, 
> > so you definitely need it running!
> 
> 
> Again, I am not using and I can't use DHCP in our network. I am using static 
> IPs. Do I still need dnsmasq?
> 

That doesn't matter, you can use dhcp and dnsmasq on virbr0, it's internal to 
dom0.


>  
> 
>  
> 
>  
> 
> > > > - Do you see domU dhcp requests in system logs (from dnsmasq) ?
> > > 
> > > 
> > > No. I always set dhcp off. I use static ips.
> > > 
> > 
> > What IP did you configure in the VM? 
> > Could you ping the gateway (dom0 IP on virbr0) from the VM?
> 
> Let's say, I am using 70.50.123.145 as a server main IP. When I create a DomU 
> and go through installation screens, I use a unique/different IP as a main IP 
> for the domain, our network gateway IP and MASK, and another unique IP for 
> our Nameserver. Does this make sense? This is what I did on Xen v3.x and it 
> worked just fine.
>  

If you attach the vm vif to virbr0, then it's NOT connected to outside/physical 
network!

> 
>  
> 
>  
> 
> > > > - After the domU is started run "brctl show" - is the domU vif 
> > > > connected to virbr0 bridge?
> > > 
> > > 
> > > It showed:
> > > 
> > > bridge name bridge id STP enabled interfaces
> > > virbr0 8000.feffffffffff yes
> > > 
> > 
> > So the VM is NOT connected to virbr0 at all!
> > Do you have xen-netback driver loaded in dom0 kernel?
> 
> 
> How can I check on that? By the way, following your tutorial with a slight 
> change, I am using i686 machine; I ran these commands to install Dom0:
> 

In my reference .config xen-netback seems to be built-in, so yes, it's 
available.

What's your cfgfile for the domU ? which bridge are you attaching the vif?


> 
>  
> 
> > > > - Run "tcpdump -i virbr0 -nn" - do you see the traffic from the vm?
> > 
> > 
> > Did tcpdump show any traffic?
> > 
> > 
> > > > - Does the domU get an IP? 
> > > 
> > > Nope.
> > > 
> > > Why Xen v4.x is so buggy and difficult to deal with? I didn't have these 
> > > problems using version 3.x. Does that mean v4 in still in beta?
> > > 
> > 
> > 4.x is not in beta. 
> > 
> > When building a platform on your own, you need to understand
> > how things work and configure everything properly.
> 
> 
> Sure. By the same token, the system, any system, doesn't have to complicated 
> to configure. Any system should be fairly easy, even for a newbie, to install 
> and configure. Do we agree on that?
> 

Of course, I agree with that.
Btw if you need something easy to set up, try XCP 1.0.

>  
> 
> Thank you and I really appreciate your help.                                  
>   
>

Hopefully it helps,

-- Pasi


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