network configuration for centos installed as virtual OS

i have installed centos6.2 as virtual OS on ubunutu 10.04
using this command

$ virt-install --connect qemu:///system -n mycentos3 -r 1024 -l '/home/sudi/Downloads/CentOS-6.2-i386-bin-DVD1(1).iso' --disk path=/var/lib/libvirt/images/mycentos3.img,size=8 --hvm --accelerate --network=bridge:virbr0

NOTE:i did minimal installation of centos

how do i configure network on centos
i tried to change the network scripts file thats is in

/etc/sysconfig/network.scripts/ifcfg-eth0

by specifying ipaddress and netmask of virbr0
also i have set default gateway for this virtual os centos
/etc/sysconfig/network

even after doing all this network is NOT enabled on centos
i pinged default gateway it says network is unreachable

i want to configure net using command line only how do i do it?
what changes i need to do?

hey guys my network is enabled on centos which is my guest virtual machine
i changed /etc/sysconfig/network-scripts/eth0
its like i removed the old ipaddress and netmask because i wanted ipaddr in centos to be dhcp configured
and jus added the BRIDGE="virbr0" in eth0 interface file
save and exit and
#ifconfig eth0 up
#dhclient eth0

now i able to ping my host os i.e ubuntu

net is properly configured on virtual machine centos.