I've been handed a domain with c.150k DNS records in it for a total of 100k machines. The DNS records are all in a single forward lookup zone on the same domain and just to be helpful, there is no reverse lookup zone.
Since Scavenging and Ageing is not an option (just my luck!), I need to find an easy way to kill off a load of stale records.
Simplest starting point for me was to look to delete all records which have a timestamp older than a year (roughly 2700 records) - but some of them are still responding to ping.
Odds are this is because we use DHCP and the IPs have since been given to new hosts.
Normally a reverse lookup zoen would come in real handy about now so that I could look for multiple registrations for an IP, but as i said before - there isn't one.
Anyone know off the top of your heads a simple way to look for duplicates? I have considered a full export to CSV from DNS and start sorting & filtering, but for over 2k records, I was hoping for something a little easier.
Also, due to the crappy nature of some of the kit we run, just deleting the records and allowing a re-registration to happen is not an option!
EDIT: not all machines are AD joined, so an AD/DNS comparisson is out of the question.
EDIT 2: Upvotes all round, some really good suggestions here! I've already started work on exports and comapres in Excel, have a ping fo each IP/Host in progress logging to a test file to see what is and isnt real and am waiting on change approval for a packet capture to start realtime monitoring. Those scripts are also useful, and while I am not going to use them in their current format, they have given me a good basis for wiritng my own stuff. Thanks everyone!