Red Hat ENTERPRISE LINUX 5 - VIRTUALIZATION GUIDE Manual page 166

Chapter 10. Pre-Red Hat Enterprise Linux 5.4 Xen networking
• Edit the configuration to suit your local needs and requirements. The following parameters are likely
the ones you want to modify:
• The interface parameter allows dnsmasq to listen for DHCP and DNS requests only on
specified interfaces. This could be dummy interfaces but not your public interfaces as well
as the local loopback interface. Add another interface line for more than one interface.
interface=dummy0 is an example which listens on the dummy0 interface.
• dhcp-range to enable the integrated DHCP server, you need to supply the range of
addresses available for lease and optionally a lease time. If you have more than one
network, you will need to repeat this for each network on which you want to supply DHCP
service. An example would be (for network 10.1.1.* and a lease time of 12hrs): dhcp-
range=10.1.1.10,10.1.1.50,255.255.255.0,12h
• dhcp-option to override the default route supplied by dnsmasq, which assumes the
router is the same machine as the one running dnsmasq. An example would be dhcp-
option=3,10.1.1.1
• After configuring dnsmasq you can copy the script below as xenDNSmasq to /etc/init.d
• If you want to automatically start dnsmasq during system boot you should register it using
chkconfig(8):
chkconfig ---add xenDNSmasq
Enable it for automatic start up:
chkconfig ---levels 345 xenDNSmasq on
• To configure dnsmasq to restart every time NetworkManager detects a change in connectivity you
can use the supplied script nm-dnsmasq.
• Copy the nm-dnsmasq script to /etc/NetworkManager/dispatcher.d/
• The NetworkManager dispatcher will execute the script (in alphabetical order if you have other
scripts in the same directory) every time there is a change in connectivity
• dnsmasq will also detect changes in your /etc/resolv.conf and automatically reload them (that
is, if you start up a VPN session for example).
• Both the nm-dnsmasq and xenDNSmasq script will also set up NAT if you have your virtualized
guests on a hidden network to allow them access to the public network.
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