networking - Share Ethernet connection with second NIC (SmartTV) - Ask Ubuntu

i running ubuntu 16.04 , having trouble sharing wired internet connection smarttv.

my setup single on-board gigabit port (enp3s0) , separate 100mbit pcie card (enp6s0).

the enp3s0 connected directly rj45 socket in wall. connects dchp , works flawlessly.

i wish allow smarttv, connected via cat5e cable second nic enp6s0, have full access internet connection.

the tv samsung ue55hu7500. it's quite limited settings can change regarding networking. can set "get settings automatically" or enter values ip address, subnet mask, gateway , dns server.

setting automatic , connecting tv wall works fine. know can fixed switch, right that's not option.

i have been trying while limited networking skills not helping. can provide me simple explanation of how working.

if using gui: (only works ipv4)

1. go in network connections setting
2. click add
3. select ethernet click create
4. use drop-down list device option enp6s0, or desired device.
5. click ipv4 settings tab
6. click on drop-down box beside method, , change shared other computers
7. click save, close

note: the tv, in case, not ip address registered router. still able access other lan computers & internet, other computers can't (without tunneling) access it.