[CentOS] Help Requested: KVM VM configuration on Centos 6.3

Hello

I am trying to install KVM based VMs on my machine. First
Timer...little idea on actually configuring related networking related
issues. Am planning to follow this howto:
http://www.howtoforge.com/virtualization-with-kvm-on-a-centos-6.3-server

My trial machine is a server cum desktop with two network ports..eth0
is normally used for LAN & Internet access...eth1 is reserved for use
with LTSP which is to be configured later.  I need my VMs to be
reachable from the internet by ssh & vnc etc. required ports will be
forwarded from the Internet router.

I propose to use subnet 10.0.1.0/24 for my virtual machines. Can
someone please advise the content of bridge configuration file at
/etc/sysconfig/network-scripts/ifcfg-br0, as given in the howto? The
two bridges ltspbr0 & virbr0 shown below, are created by packages
installed & not by me, so if any modifications are required in
them...I need to know. Also, please advise if it is possible to get
the VMs to use a 3G usb device for Internet access  through the host
machine Network Manage, in case Internet access through eth0 is down?
Though this is not a priority at this stage, as I am just learning to
use my first VM, but I'd like this feature if it is not too difficult.

With regards.
Sanjay.


ifconfig output:

[root at Swayam ~]# ifconfig
eth0      Link encap:Ethernet  HWaddr E0:69:95:77:A7:F3
          inet addr:10.0.0.101  Bcast:10.0.0.255  Mask:255.255.255.0
          inet6 addr: fe80::e269:95ff:fe77:a7f3/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:5120 errors:0 dropped:0 overruns:0 frame:0
          TX packets:5506 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:4205139 (4.0 MiB)  TX bytes:684760 (668.7 KiB)
          Interrupt:20 Memory:fe600000-fe620000

eth1      Link encap:Ethernet  HWaddr 00:60:52:0C:0B:DE
          UP BROADCAST MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:0 (0.0 b)  TX bytes:0 (0.0 b)
          Interrupt:16

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:155 errors:0 dropped:0 overruns:0 frame:0
          TX packets:155 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:59335 (57.9 KiB)  TX bytes:59335 (57.9 KiB)

ltspbr0   Link encap:Ethernet  HWaddr AE:41:A9:3D:FE:A3
          inet addr:172.31.100.254  Bcast:172.31.100.255  Mask:255.255.255.0
          inet6 addr: fe80::ac41:a9ff:fe3d:fea3/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:73 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:0 (0.0 b)  TX bytes:14407 (14.0 KiB)

virbr0    Link encap:Ethernet  HWaddr 52:54:00:86:BD:15
          inet addr:192.168.122.1  Bcast:192.168.122.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:45 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:0 (0.0 b)  TX bytes:11636 (11.3 KiB)