Author: K.Kirkpatrick (2 May 05 11:01am)
Your thinking of your missing A records as if they are loose ends... they aren't
It no different than having an unlisted phone number.
You still have the phone, and the phone is still reachable, but the phone number isn't published.
An A record is just a published reference that makes it easier to look your up.
Not having one doesn't do anything.
You need not even have a domain to run a server... Just because you don't name your house, doesn't make the house disappear off the street.
A domain is just a convenience, and an A record is just a way to publish the relationship between your Domain and your IP addy.
Not having an A record for a subdomain is common.
Don't be concerned about it causing an exploit problem... not listing it, just makes it that much more secure. It will not interfer with your Domain name, or the listings for your Domain.
I didn't name my back bedroom, but that doesn't keep it hidden from me... strangers however don't really need to know I have a back bedroom... so, I don't publish a map to it.