Hello Rodney:

You'll be pleased to learn that we've addressed this issue in our upcoming maintenance release, 4.3.6 due out July 31st, and in 4.4.0 release date is TBD.

We have modified the DDNS support initialization such that the DNS related ports will only be opened:

1. By the server (dhcpd) at startup if ddns-update-style is not "none"
2. By dhclient only when and if it first attempts to do an update
3. Never by dhcrelay. 

Prior to this all three always did the initialization at startup when DDNS support was compiled in.

Thank you for reporting this issue to us.  Typically we like to recognize our contributors by citing them in the release notes.  If you would like to be so noted please respond with how you'd like to be identified.

Sincerely,

Thomas Markwalder
ISC Software Engineering