Re: Networking in KVM

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Paul,


On Thu, Mar 17, 2016 at 5:47 PM, Digimer <lists@xxxxxxxxxx> wrote:
On 17/03/16 04:47 PM, paul.greene.va@xxxxxxxxxxx wrote:
> Thanks, I followed the 2nd article, and it got the existing virtual
> machines communicating with each other.

Right, so your VMs are on the same bridge group now (at Layer2 of OSI).
 
>
> However, any new virtual machines I created after making the changes
> can't communicate with anything, they can't even get out to the
> internet, even if I manually set the IP address info. Any suggestions on
> that?
>
> Paul

Have you verified connectivity to the VMs' default gateway?
Does the ARP (address resolution protocol) process succeed?
arp -a | grep <Default_Gateway_IP_here>

You may not have a NIC connected to your physical network in that bridge group.
If so you need to modify your network-scripts to make that happen automatically on boot.
You do not necessarily need an IP address on your bridge interface unless the VM host is acting as a router (default gateway).

Here's an example:
~]# cat /etc/sysconfig/network-scripts/ifcfg-XX_br0 
DEVICE=XX_br0
TYPE=Bridge
BOOTPROTO=static
_ONBOOT_=yes
DELAY=0
NM_CONTROLLED=no

You can temporarily add an interface to the bridge group for testing purposes though.
brctl addif <bridge> <interface>
 

Check that they're using your static bridge. 'virsh dumpxml <vm>' will
have a section like:

====
    <interface type='network'>
      <mac address='52:54:00:71:20:fa'/>
      <source network='bcn_bridge1' bridge='bcn_bridge1'/>
      <target dev='vnet2'/>
      <model type='e1000'/>
      <alias name='net2'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x05'
function='0x0'/>
    </interface>
====

That tells you that the interface is MAC '52:54:00:71:20:fa' is "plugged
in" to the bridge 'bcn_bridge1'. If that doesn't connect to the right
bridge, then you need to change it (virt-manager has a simple to use GUI
for this, or you can use 'virsh edit <vm>' if you're comfortable editing
XML).

An additional command to run to verify your Ethernet bridge(s) operation is:
brctl show
brctl show <bridge>

~]# brctl show XX_br0
bridge name bridge id STP enabled interfaces
XX_br0 8000.00151713fdbc no p1p1
vnet0
vnet1
vnet11
vnet12
vnet13
vnet19
vnet2
vnet4
vnet6
vnet7


--
---~~.~~---
Mike
//  SilverTip257  //
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