+OS=$1
+
+if [ "${OS}" == "ubuntu1404" ]; then
+ VIRL_TOPOLOGY=double-ring-nested.trusty
+ VIRL_RELEASE=csit-ubuntu-14.04.4_2016-10-07_1.3
+elif [ "${OS}" == "ubuntu1604" ]; then
+ VIRL_TOPOLOGY=double-ring-nested.xenial
+ VIRL_RELEASE=csit-ubuntu-16.04.1_2016-12-19_1.6
+elif [ "${OS}" == "centos7" ]; then
+ VIRL_TOPOLOGY=double-ring-nested.centos7
+ VIRL_RELEASE=csit-centos-7.3-1611
+fi