Refer to the IS-IS configuration exhibit.

This is the typical IS-IS configuration of the routers in an AS using IS-IS as the IGP. This AS is in the transition phase of integrating IPv6 into the network. During this transition phase, some of the routers within the AS might be running IPv4 only, some might be running IPv6 only, and others might be running both IPv4 and IPv6. To avoid any black holes for the IPv6 traffic, which configuration change can be made?