The 2.6 SOHO networks has a ppt slide called IPV4 private and public IP addresses in which the class B in private addressing has incorrect info, instead of 10.0.0.0 to 10.255. 255.255, it will be 172.16.0.0 to 172.31.255.255, so by mistakenly from your end the Class A range is repeated in Class B as well. The 2nd mistake is that in 1 slide which is so called as configuring private ipv6, the ipv6 address and the default gateway are given as same, please correct it.
Thank You