[CentOS-virt] Centos 6.2 / KVM troubles with network

On Sat, Jan 14, 2012 at 8:41 AM, Radek Bursztynowski <
radek at bursztynowski.waw.pl> wrote:

> **
> Dnia 2012-01-14, sob o godzinie 15:08 +0100, Dennis Jacobfeuerborn pisze:
>
> On 01/14/2012 02:59 PM, Radek Bursztynowski wrote:
> > Hi,
> >
> > I have installed CentOS 6.2 x86_64 and KVM/Qemu and I have some troubles
> > with network.
> >
> > The first case:
> > -----------------
> >
> > The configuration is:
> > - CentOS 6.2 (hardware machine) has one Ethernet interface with static IP
> > address (eth0).
> > - Virtual machine has bridge network interface with eth0 interface on
> > CentOS 6.2. This bridge is created using wizard integrated with virt-manager.
> > - Bridge interface on virtual machine receives IP addres from DHCP server.
> > IP address is received well.
> > - All firewalls and SELinux are closed.
> >
> > Virtual machine has no any connection with CentOS 6.2 hardware machine, and
> > CentOS 6.2 has no any connection with virtual machine. But every others
> > machines have all connection with both virtual and CentOS 6.2 machine.
> >
> > The question: Why?
> >
> > The second case:
> > ----------------------
> >
> > The configuration is:
> > - On CentOS 6.2 (hardware machine) I created bridhe (br0) with eth0
> > hardware interface. Two situations:
> > + I force two different IP addresses for eth0 and br0 interfaces - there no
> > any connection with this server. So I don't test this case.
> > + I forced one IP addres for both eth0 and br0 interfaces. ifconfig shows
> > that eth0 has no IP address, br0 has IP address. So, I test this case.
> > - I use Red Hat documentation:
> > http://docs.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/5/html-single/Virtualization/index.html#sect-Virtualization-Network_Configuration-Bridged_networking_with_libvirt)
> > - On virtual machine I created bridge connection with br0 interface on
> > CentOS 6.2.
> > - All machines have all connections.
> > - All firewalls and SELinux are closed.
> >
> > NFS server on CentOS 6.2 (hardware machine) doesn't serve exported file system.
> >
> > The questions:
> > 1. Is it proper that eth0 has no IP addres and bridge (br0) interface has?
> > 2. What about my NFS? NFS server worked well before starting virtualization.
> >
> > Who can me help with my troubles?
>
> You say you create bridge interfaces in your virtual machines. Why? Usually
> you don't do that you create a bridge only on the host.
>
> You also say you "forced" one IP address for both eth0 and br0. There is no
> need to force anything. eth0 shouldn't have an IP but br0 should have this
> IP instead.
>
> Regards,
>    Dennis
> _______________________________________________
>
>  Dennis,
>
> Thanks for interesting. Few words explanation.
> I have one network segment, and I try to joint virtual machines to this
> segment. So my hardvare machine has 192.168.0.1 address, gateway is
> 192.168.0.254, netmask = 255.255.255.0.
>
> Regarding bridge on my virtual machine. When I started virtualization I
> had NAT only in another network segment. So, I look for solution adding
> virtual machines to my base network segment. Previously I used VMware
> Server, and it was proper solution.
>
> Regarding my force one IP addres for both interface. I used this solution
> because eth0 has no any IP addres and I couldn't find CentOS 6.2 server in
> the network. Using exactly Red Hat configuration I have:
>
> # more ifcfg-eth0
> DEVICE=eth0
> TYPE=Ethernet
> BOOTPROTO=none
> IPADDR=192.168.0.1
> NETMASK=255.255.255.0
> PREFIX=24
> GATEWAY=192.168.0.254
> DNS1=192.168.0.199
> DNS2=194.204.159.1
> DNS3=194.204.152.34
> DEFROUTE=yes
> IPV4_FAILURE_FATAL=yes
> IPV6INIT=no
> NAME=eth0
> ONBOOT=yes
> BRIDGE=br0
> MTU=9000
> DOMAIN=bursztynowski.waw.pl
> UUID=5fb06bd0-0bb0-7ffb-45f1-d6edd65f3e03
>
> # more ifcfg-br0
> DEVICE=br0
> TYPE=Bridge
> BOOTPROTO=dhcp
> #IPADDR=192.168.0.1
> #NETMASK=255.255.255.0
> #PREFIX=24
> #GATEWAY=192.168.0.254
> #DNS1=192.168.0.199
> #DNS2=194.204.159.1
> #DNS3=194.204.152.34
> ONBOOT=yes
> DELAY=0
>
> (previous configuration br0 was:
> BOOTPRO=static
> and with no '#' characters. Then all worked excluding NFS.
>
>
> # ifconfig
> br0       Link encap:Ethernet  HWaddr 00:50:8D:94:2F:B7
>           inet addr:192.168.0.92  Bcast:192.168.0.255  Mask:255.255.255.0
>           inet6 addr: fe80::250:8dff:fe94:2fb7/64 Scope:Link
>           UP BROADCAST RUNNING MULTICAST  MTU:9000  Metric:1
>           RX packets:16 errors:0 dropped:0 overruns:0 frame:0
>           TX packets:26 errors:0 dropped:0 overruns:0 carrier:0
>           collisions:0 txqueuelen:0
>           RX bytes:3034 (2.9 KiB)  TX bytes:4313 (4.2 KiB)
>
> eth0      Link encap:Ethernet  HWaddr 00:50:8D:94:2F:B7
>           inet6 addr: fe80::250:8dff:fe94:2fb7/64 Scope:Link
>           UP BROADCAST RUNNING PROMISC MULTICAST  MTU:9000  Metric:1
>           RX packets:57255 errors:0 dropped:0 overruns:0 frame:0
>           TX packets:60263 errors:0 dropped:0 overruns:0 carrier:0
>           collisions:0 txqueuelen:1000
>           RX bytes:21481457 (20.4 MiB)  TX bytes:15768417 (15.0 MiB)
>           Interrupt:23 Base address:0x8000
>
> lo        Link encap:Local Loopback
>           inet addr:127.0.0.1  Mask:255.0.0.0
>           inet6 addr: ::1/128 Scope:Host
>           UP LOOPBACK RUNNING  MTU:16436  Metric:1
>           RX packets:30723 errors:0 dropped:0 overruns:0 frame:0
>           TX packets:30723 errors:0 dropped:0 overruns:0 carrier:0
>           collisions:0 txqueuelen:0
>           RX bytes:92725098 (88.4 MiB)  TX bytes:92725098 (88.4 MiB)
>
> Should I replace static and dhcp addresses between eth0 and br0 interface?
>
> Regards,
> Radek
>
>
>
>
>
>
>
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>
>
To use bridging on the virtual host you have to assign the IPs to br0 and
then add "Bridge=br0" to ifcfg-eth0.  I have working examples here,
http://itscblog.tamu.edu/startup-guide-for-kvm-on-centos-6/.
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