ipv6 address subnet prefix length default gateway
1 In IPv6 address, type 2001:db8:1::3. 2  In Subnet prefix length, type 64. 3  In Default gateway, type 2001:db8:1::2. 4  Click Use the following DNS server addresses, and in Preferred DNS server, type 2001:db8:1::1. In IPv6 address, type 2001:db8:1::3. 2  In Subnet prefix length, type 64. 3  In Default gateway, type 2001:db8:1::2. 4  Click Use the following DNS server addresses, and in Preferred DNS server, type 2001:db8:1::1.