While installing RAC on virtualBox guests (linux), related docs declare that SCAN addresses should not be defined in the hosts file.Beacuse of round-robin resolution cannot be simulated using a local host file ,The Single Client Access Name (SCAN) should be defined in the DNS and round-robin between one of 3 addresses , which are on the same subnet as the public and virtual IPs.
I am using virtualbox for testing purposes on various guests, and sometimes DNS server is needed.Not to struggle with complex DNS configuration , Dnsmasq is the best solution.Following steps are used to install,configure,start Dnsmasq service.
On seperate linux guest , Dnsmasq is installed from yum
# yum install dnsmasq
Start Dnsmasq service
# service dnsmasq start
To start Dnsmasq service automatically on reboot
# chkconfig dnsmasq on
Dnsmasq will use entries of the "/etc/hosts" to resolve.
"/etc/hosts" file contains following entries on the server running Dnsmasq service provide acting live DNS server by resolving these entries.
192.168.0.91 testracclusterscan.localdomain testracclusterscan
192.168.0.92 testracclusterscan.localdomain testracclusterscan
192.168.0.93 testracclusterscan.localdomain testracclusterscan
192.168.0.71 node1.localdomain node1
192.168.0.72 node2.localdomain node2
Guests which will use DNS server for name resolution , need to have "/etc/resolve.conf" file configured DNS server
nameserver 192.168.0.10
search localdomain
Detail information about SCAN:
http://www.oracle.com/technetwork/database/clustering/overview/scan-129069.pdf
source : http://www.oracle-base.com/articles/linux/dnsmasq-for-simple-dns-configurations.php
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