When ARIN began operations, one of the tasks that it took over from the InterNIC was the generation of the zone file for the in-addr.arpa domain. In order to correct long-standing issues with the data in the zone file, new software is being deployed. ARIN policy states that allocation subscribers with networks of /16 or shorter prefix are responsible for maintaining all in-addr.arpa domain records for reassignments within the block. They must also provide to ARIN the host names of the nameservers hosting any delegations. ARIN will continue to host domain records for delegations of networks with prefixes longer than /16. The in-addr.arpa zone will contain delegations for any /8 containing nameservers within ARIN's database. For address space not covered via these delegations, the in-addr.arpa domain will contain delegations for /16's with nameservers. For address space still not delegated and as mentioned above, the in-addr.arpa domain will contain delegations of /24's for networks longer than a /16 containing in-addr nameservers. In all cases, the most specific reassignment with nameservers at each octet boundary will prevail. ARIN is making every effort to ensure that any impact from these changes will not disrupt in-addr.arpa name services. If you have concerns whether in-addr.arpa name services will be impacted for your networks, please review examples of the changes to occur at: http://www.arin.net/inaddr/inaddr-examples.txt If you still have concerns after reviewing these examples, please direct specific questions about your networks to inaddr@arin.net. We have tentatively scheduled implementation of the new process for late May or early June. A specific date will be announced several days prior to the cut-over on both the arin-announce and nanog mailing lists. Regards, Ginny Listman Director of Engineering ARIN