[CentOS-virt] Finally switching from Xen to KVM - question about networking

On 6/10/2014 3:09 PM, Zoltan Frombach wrote:
> Steve,
>
> Try the following config.
>
> On your host:
>
> /etc/sysconfig/network-scripts/ifcfg-eth0    :
>
> DEVICE=eth0
> BOOTPROTO=none
> ONBOOT=yes
> NM_CONTROLLED=no
> TYPE=Ethernet
> HWADDR=xx:xx:xx:xx:xx:xx    <- put your physical NIC's MAC address here
> BRIDGE=br0
> USERCTL=no
> IPV6INIT=no
> IPV6_AUTOCONF=no
>
>
> /etc/sysconfig/network-scripts/ifcfg-br0    :
>
> DEVICE=br0
> BOOTPROTO=static
> ONBOOT=yes
> NM_CONTROLLED=no
> TYPE=Bridge
> IPADDR=10.0.5.16
> NETMASK=255.255.255.0   <- you may need to adjust this to your network
> GATEWAY=10.0.5.1
> DNS1=8.8.8.8
> DNS2=8.8.4.4
> PEERDNS=yes
> DELAY=0
> STP=off
> USERCTL=no
> IPV6INIT=no
> IPV6_AUTOCONF=no
>
>
> Restart networking on the host.
>
> Then inside you VM:
>
> /etc/sysconfig/network-scripts/ifcfg-eth0    :
>
> DEVICE=eth0
> BOOTPROTO=static
> ONBOOT=yes
> NM_CONTROLLED=no
> TYPE=Ethernet
> HWADDR=xx:xx:xx:xx:xx:xx    <- it must be a unique MAC address for 
> your VM
> IPADDR=10.0.5.17
> NETMASK=255.255.255.0     <- you may need to adjust this to your network
> GATEWAY=10.0.5.1
> DNS1=8.8.8.8
> DNS2=8.8.4.4
> PEERDNS=yes
> USERCTL=no
> IPV6INIT=no
> IPV6_AUTOCONF=no
>
>
> Then in Virtual Machine Manager make sure that your VM's NIC is 
> connected to the br0 bridge, like this:
>
> Network Source: Specify shared device name
>       Bridge Name: br0
>
>
>
> On 6/10/2014 8:16 PM, Steve Campbell wrote:
>> On 6/10/2014 12:43 PM, Digimer wrote:
>>> On 10/06/14 12:38 PM, Steve Campbell wrote:
>>>> On 6/10/2014 12:05 PM, Digimer wrote:
>>>>> On 10/06/14 11:46 AM, Steve Campbell wrote:
>>>>>> On 6/10/2014 10:46 AM, Digimer wrote:
>>>>>>> On 10/06/14 10:03 AM, Steve Campbell wrote:
>>>>>>>> I had so much trouble putting Centos 6 guest VMs on a Centos 5 
>>>>>>>> host
>>>>>>>> that
>>>>>>>> I finally switched to a Centos 6 host.
>>>>>>>>
>>>>>>>> I've not needed more that test VMs, so I've used Virtual Machine
>>>>>>>> Manager
>>>>>>>> on the old system, which worked pretty well, so I decided to
>>>>>>>> create my
>>>>>>>> first KVM guest machine. I noticed when I created it, I only 
>>>>>>>> had the
>>>>>>>> options of NAT for my network interface, so I used that (obvious).
>>>>>>>>
>>>>>>>> Well, after starting the VM, I find I don't have connectivity with
>>>>>>>> that
>>>>>>>> interface. Reading, I find examples where I need to create bridges
>>>>>>>> perhaps. Xen did most of this for me, so it's a little new to me.
>>>>>>>>
>>>>>>>> Can anyone throw me a clue, please?
>>>>>>>>
>>>>>>>> steve campbell
>>>>>>> Setting up a bridge is not that hard, and it will give your VMs
>>>>>>> direct
>>>>>>> access to the outside world, and host <-> VM access just fine as
>>>>>>> well.
>>>>>>>
>>>>>>> Here is a link showing how to setup a bridge connected to a bond
>>>>>>> device. Ignore the bond and pretend it is a straight ethX device:
>>>>>>>
>>>>>>> https://alteeve.ca/w/AN!Cluster_Tutorial_2#Configuring_our_Bridge.2C_Bonds_and_Interfaces 
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>> The host has a device named virbr0 that is installed during system
>>>>>> installation. It also has a network device vnet0. There are no
>>>>>> files in
>>>>>> /etc/sysconfig/network-scripts for these.
>>>>>>
>>>>>> Shouldn't I be able to use the virbr0 virtual bridge for this? I've
>>>>>> tried setting up the VM's device with all of the options that is
>>>>>> listed,
>>>>>> but to no avail.
>>>>>>
>>>>>> Should I need to set up another bridge for this?
>>>>>>
>>>>>> And thanks for the link.
>>>>>>
>>>>>> steve
>>>>> virbr0 is created and managed by libvirtd. If you open Virtual 
>>>>> Machine
>>>>> Manager, connect to localhost and then double-click on 'localhost',
>>>>> you will see a tab for creating/managing bridges (NAT'ed, generally).
>>>>> I disable 'virbr0' as NAT'ing is generally not what I want.
>>>>>
>>>>> The 'vnetX' devices are dynamically created to link a VM's interface
>>>>> to a bridge. Think of them as virtual network cables. They get 
>>>>> created
>>>>> and destroyed as needed.
>>>>>
>>>>>
>>>> Sorry, but I'm confused:
>>>>
>>>> My host server has a real NIC and IP address with a real gateway to 
>>>> the
>>>> outside:
>>>> virtbr0 IP: 192.168.122.1
>>>> Host IP: 10.0.5.16
>>>> Gateway IP: 10.0.5.1
>>>> on eth0 and this works
>>>>
>>>> My VM server has all fake stuff currently:
>>>> Host IP: 10.0.5.17
>>>> Gateway IP: 10.0.5.1
>>>> on eth0 and this is like NIC without a cable.
>>>>
>>>> So I need to create a bridge device on both the host and VM (lets 
>>>> say I
>>>> name it br1). I change the eth0 config file on both host and VM to 
>>>> point
>>>> to br1 and give the br1 config file on both host and VM the correct 
>>>> IP.
>>>> But won't this just let the two talk to each other. How will the VM
>>>> server get outside?
>>>>
>>>> steve
>>> The bridge is created only on the host. Think of the bridge as being
>>> like a virtual switch. When a VM is created, you tell it to connect to
>>> the bridge, similar to how you would plug a physical wire into a real
>>> switch. That provides the link to the network, and then you configure
>>> the virtual server's network just as if it was a real network.
>>>
>>> On the host, you don't set the IP on the ethX device, instead you tell
>>> ethX to connect to the bridge (look at 'bond2' in the link above for
>>> the 'BRIDGE="..."' line). Then you move the host's IP address/config
>>> to the bridge itself (look at the 'vbr2' in the link above).
>>>
>>> If you're still stuck, tell me the IP addresses you want to set in the
>>> host and VM and I'll see if I can bang out a couple sample 'ifcfg-X'
>>> files.
>>>
>> I'm running into some problems with my config files where I get a
>> message that says the network can't determine my interface names. I'll
>> look further, but the IPs above are what I need. 10.0.5.1 is a firewall
>> that NATs the 10.0.5.0/24 network to another outside public firewall.
>>
>> Thanks
>> steve
>> _______________________________________________
>> CentOS-virt mailing list
>> CentOS-virt at centos.org
>> http://lists.centos.org/mailman/listinfo/centos-virt
>>
>
Stuck in a rut now. Restarting the network indicates :

Device eth0 does not seem to be present, delaying initialization.

I thought it might be due to the fact I didn't have the "TYPE" in the 
ifcfg-eth0 file, but after adding that, I still get the error.

I'm using the same hardware address that was in the original eth0 file. 
My bridge device starts fine, but I'll tailor it to your specs.

Thanks
steve