IPv6 - RA suppression command
By default, in an IPv6 environment, a router will not send IPv6 router advertisements (RA) on a tunnel interface. However, when employing IPv6 Intra Site Automatic Tunnel Addressing Protocol (ISATAP), it is necessary to disable this default behavior.
In Cisco IOS versions before 12.4(2)T, the command to achieve this is the following:
ipv6 nd suppress-ra
This is applied to the tunnel interface on the headend of the ISATAP tunnel.
For Cisco IOS versions 12.4(2)T and later, the command has changed to the following:
ipv6 nd ra suppress
again, applied to the tunnel interface on the headend of the ISATAP tunnel.