DNS Zone has entries dynamicaly added

My DNS is seemingly setup OK, NSlookup tests tell me that.
What I don’t understand is how and why entries automatically get added to my zone
list in DNS.

These entries are from our road reps who dial in via our carrier over a
public dial-in access. They get assigned a very short lease IP address,
10.10.5.X. This ip address can be used again by the next guy to dial-in to
the network almost immediately.

Im asking this because we are having netlogon issues “Access Denied” and
these entries don’t seem right to me.
Your input is welcome.

T.