I walked the tree manually <see attached>. Two problems.
1. SDN.IECC.COM does not answer authoritatively.
Odd, it's supposed to be authoritative and it's authoritative now. Something was very strange over the weekend. In case it's not obvious, light.lightlink.com is my DNS mirror, who's also supposed to be authoritative, ivan.iecc.com is my old server I'm trying to turn off, sdn.iecc.com is the new one.
2. In our database, you have IVAN.IECC.COM as the primary NS that we delegate to, for 42.31.208.in-addr.arpa. In turn, IVAN delegates to SDN.IECC.COM. For the sake of efficiency, you may want to ask your ISP to send an e-mail to dns@sprint.net and ask our NOC to change this in our database to SDN.IECC.COM. Of course, once SDN.IECC.COM is answering authoritatively again.
Thanks, will do. Regards, John Levine, johnl@iecc.com, Primary Perpetrator of "The Internet for Dummies", Information Superhighwayman wanna-be, http://iecc.com/johnl, Sewer Commissioner Finger for PGP key, f'print = 3A 5B D0 3F D9 A0 6A A4 2D AC 1E 9E A6 36 A3 47