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18.17. Configuración de portátiles

The task of configuring your RHEL 5.1 loaded laptop for use on a network environment, presents a number of potential challenges. Most WiFi and wired connections switch constantly during any given day, and Red Hat Virtualization assumes it has access to the same interface consistently. This results in the system performing ifup/ifdown calls to the network interface in use by Red Hat Virtualization. WiFi cards are not the ideal network connection method since Red Hat Virtualization uses the default network interface.
The idea here is to create a 'dummy' network interface for Red Hat Virtualization to use.
This technique allows you to use a hidden IP address space for your guests and Virtual Machines. To do this operation successfully, you must use static IP addresses as DHCP does not listen for IP addresses on the dummy network. You also must configure NAT/IP masquerading to enable network access for your guests and Virtual Machines. You should attach a static IP when you create the 'dummy' network interface.
En este ejemplo, la interfaz se llama dummy0 y la dirección IP es 10.1.1.1. El script se llama ifcfg-dummy0 y está ubicado en el directorio /etc/sysconfig/network-scripts/ 
DEVICE =dummy0
BOOTPROTO=none
ONBOOT=yes
USERCTL=no
IPV6INIT=no
PEERDNS=yes
TYPE=Ethernet
NETMASK=255.255.255.0
IPADDR=10.1.1.1
ARP=yes
Usted debe enlazar xenbr0 a dummy0 para permitir la conexión de red incluso cuando se esté desconectado de la red física.
You will need to make additional modifications to the xend-config.sxp file. You must locate the ( network-script 'network-bridge' bridge=xenbr0 ) section and add include this in the end of the line: 
netdev=dummy0
You must also make some modifications to your guest's domU networking configuration to enable the default gateway to point to dummy0. You must edit the DomU 'network' file that resides in the /etc/sysconfig/ directory to reflect the example below: 
NETWORKING=yes
HOSTNAME=localhost.localdomain
GATEWAY=10.1.1.1
			
IPADDR=10.1.1.10
NETMASK=255.255.255.0
Es aconsejable activar NAT en domain0 para que domU pueda acceder a la red pública. De esta manera, incluso los usuarios de servicios inalámbricos pueden solucionar las limitaciones inalámbricas del componente de virtualización de Red Hat. para hacerlo, modifique el archivo S99XenLaptopNAT ubicado en el directorio /etc/rc3.d para que refleje el ejemplo dado a continuación: 
#!/bin/bash
#
# XenLaptopNAT  Startup script for Xen on Laptops
#
# chkconfig: - 99 01
# description: Start NAT for Xen Laptops
#
# 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
Si desea configurar la red automáticamente durante el periodo de arranque, debe crear un enlace simbólico a /etc/rc3.d/S99XenLaptopNAT
Cuando modifique el archivo modprobe.conf debe incluir estas líneas: 
alias dummy0 dummy
options dummy numdummies=1