You can have multiple reverse zones as you can have multiple forward lookup zones. At my job we have 4 different reverse zones describing 4 different IP ranges. Remember the reverse zone is to describe the IP range rather than the domain name. So if you have items in your sky.com zone that are pointing to IPs in two different ranges you can have two different reverse zones to describe each of those. Just remember that each of those reverse zones should only include the sky.com servers that are in their specific IP ranges.
Also note that DNS registration and delegation only covers your forward lookups typically. So even if your DNS registrar already has all your DNS server information you'll have to go to your ISP or Internet Carrier and tell them to also delegate the IP ranges they've assigned you to your DNS server. Otherwise lookups will stop at the IPS or Internet Carrier and return no record. For example at my company we have Network Solutions as the DNS registrar but have AT&T as our Internet Carrier. Your forward lookups will work fine even if you don't get the reverse delegation but reverse lookups won't work. Typically it takes 24 hours or more for a provider to update their records and have it propagate out.
Last edited by MensaWater; 01-22-2007 at 08:51 AM.