In a dual-stack network where ipv6 subnet alone is associated to the neutron router, the following NPE is seen when spawning a new VM.

java.lang.NullPointerException: null
at org.opendaylight.netvirt.vpnmanager.VpnUtil.getGWMacAddressFromInterface(VpnUtil.java:1373) [362:org.opendaylight.netvirt.vpnmanager-impl:0.7.0.SNAPSHOT]
at org.opendaylight.netvirt.vpnmanager.AlivenessMonitorUtils.startArpMonitoring(AlivenessMonitorUtils.java:73) [362:org.opendaylight.netvirt.vpnmanager-impl:0.7.0.SNAPSHOT]
at org.opendaylight.netvirt.vpnmanager.ArpMonitorStartTask.call(ArpMonitorStartTask.java:39) [362:org.opendaylight.netvirt.vpnmanager-impl:0.7.0.SNAPSHOT]
at org.opendaylight.netvirt.vpnmanager.ArpMonitorStartTask.call(ArpMonitorStartTask.java:18) [362:org.opendaylight.netvirt.vpnmanager-impl:0.7.0.SNAPSHOT]
at org.opendaylight.infrautils.jobcoordinator.internal.JobCoordinatorImpl$MainTask.runWithUncheckedExceptionLogging(JobCoordinatorImpl.java:401) [275:org.opendaylight.infrautils.jobcoordinator-impl:1.4.0.SNAPSHOT]
at org.opendaylight.infrautils.utils.concurrent.LoggingUncaughtThreadDeathContextRunnable.run(LoggingUncaughtThreadDeathContextRunnable.java:60) [280:org.opendaylight.infrautils.util:1.4.0.SNAPSHOT]
at java.util.concurrent.ForkJoinTask$RunnableExecuteAction.exec(ForkJoinTask.java:1402) [?:?]
at java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:289) [?:?]
at java.util.concurrent.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1056) [?:?]
at java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:1692) [?:?]
at java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:157) [?:?]