how can i acces the nrf51(nrf51422) dk from the internet using copper coap?

[Liverpool007]

I have set up raspberry pi 3 as a border router and programmed the the nrf51422 using the iot_ipv6_coap_server_pca10028 and could successfully switch on and off led3 and led4 using copper coap client on a local area network.

[Liverpool007]

in step (6) which ipv6 addresse should i assign in the last two lines of the interfaces file?