The challenge in running Red Hat Virtualization on a laptop is that most laptops will connected to the network via wireless network or wired connections. Often these connections are switched multiple times a day. In such an environment Red Hat Virtualization does not behave well as it assumes it has access to the same interface all the time and it also can perform ifup or ifdown calls to the network interface it is using. In addition wireless network cards do not work well in a Red Hat Virtualization environment due to Red Hat Virtualization's (default) bridged network usage.

This setup will also enable you to run Red Hat Virtualization in offline mode when you have no active network connection on your laptop. The easiest solution to run Red Hat Virtualization on a laptop is to follow the procedure outlined below:

Configuring a dummy network interface

Perform the following configuration steps on your host/Dom0:

Configuring NAT(network address translation) for Red Hat Virtualization

Network address translation(NAT) allows multiple network address to connect through a single IP address by intercepting packets and passing them to the private IP addresses. You can copy the following script to /etc/init.d/xenLaptopNAT and create a soft link to /etc/rc3.d/S99xenLaptopNAT. this automatically starts NAT at boot time.

#!/bin/bash
PATH=/usr/bin:/sbin:/bin:/usr/sbin
export PATH
GATEWAYDEV=`ip route | grep default | awk {'print $5'}`
iptables -F
case "$1" in
start)
	if test -z "$GATEWAYDEV"; then
	echo "No gateway device found"
    else
	echo  "Masquerading using $GATEWAYDEV"
	/sbin/iptables -t nat -A POSTROUTING -o $GATEWAYDEV -j MASQUERADE
fi
	echo "Enabling IP forwarding"
	echo 1 > /proc/sys/net/ipv4/ip_forward
	echo "IP forwarding set to `cat /proc/sys/net/ipv4/ip_forward`"
	echo "done."
	;;
*)
echo "Usage: $0 {start|restart|status}"
;;
esac

Configuring dnsmasq for the DNS, DHCP and tftpboot services

One of the challenges in running Red Hat Virtualization on a laptop (or any other computer which is not connected by a single or stable network connection) is the change in network interfaces and availability. Using a dummy network interface helps to build a more stable environment but it also brings up new challenges in providing DHCP, DNS and tftpboot services to your virtual machines/guests. The default DHCP daemon shipped with Red Hat Enterprise Linux and Fedora Core will not listen on dummy interfaces, your DNS forwarded information may change as you connect to different networks and VPNs.

One solution to the above challenges is to use dnsmasq which can provide all of the above service in a single package and will also allow you to control its service only being available to requests from your dummy interface. Below is a short write up on how to configure dnsmasq on a laptop running Red Hat Virtualization: