You may be aware that as per the Department of Telecom (DOT), Government of India roadmap for migration to IPv6 "All new registrations of .IN domain name is to be compulsorily on dual stack with effect from 1st January, 2014. The entire .IN domain should migrate to IPv6 (dual stack) latest by June 2014 as mandated by the Government.
Accordingly, .IN registry has extended support for connections to the registry hosts (EPP, WHOIS and Web) on IPv6 starting 15th May 2014 00:00 IST [14 May 2014, 18:30 UTC].
IPv6 subnets can be a combination of up to 3 subnets of /128, /64, /48. Registrars can submit IPv6 subnets as they see fit, as long as the total number of both IPv4 and IPv6 subnets stays within the limit of total 3 subnets.
Also, as explained during the recent Meeting of NIXI with Registrars in Mumbai, on 3rd April 2014, whenever registrars with dual stack enabled hosts try to connect to the .IN registry, the IPv6 address will usually be selected over the IPv4 address for the connection. Therefore all such registrars who intend to connect to the .IN registry using an IPv6 address, need to contact Technical Support to reflect your IPv6 addresses in the white list so that the .IN Registry firewall does not block it. If you have not submitted your IPv6 address to Technical Support for inclusion in the list of allowed IPs for your registrar, the registry will refuse a connection and your client will be unable to establish a connection with the registry. You may implement RFC 6555 in your client to address this issue.
As always, please contact .IN Tech Support if you have any questions regarding the IPv6 connectivity for .IN Registry.
.IN Technical Support