Draytek Vigor2860 series User Manual page 131

6rd Prefix
6rd Prefix Length
After finished the above settings, click OK to save the settings.
Below shows an example for successful IPv6 connection based on 6rd mode.
Type the 6rd IPv6 address.
Type the IPv6 prefix length for the 6rd IPv6 prefix in
number of bits.
117
Vigor2860 Series User's Guide