To the best of my knowledge, you can setup the CMS HA without DNS. you can have the CMS in HA seperated over the WAN hence the confirmation.
for ACD, the IP should be reachable & for HA (data sync etc.) primary CMS should be able to reach the HA CMS, you can do it over the IP entry in host table.
Success is the ability to go from one failure to another failure with no loss of enthusiasm & energy - Winston Churchill