The following steps show you how to do settings to allow access 6lbr from Internet. Let's say we have a Internet router (mine is Asus RT-N12HP_B1) and the LAN address is 192.168.1.xxx.
1. Access to 6lbr web page (http://[bbbb::100]) inside LAN and go to configuration page of 6lbr. Select IP64: on, DHCP: off, input a IPv4 address 192.168.1.2 (this might be different if you don't use 192.168.1.xxx as LAN address on your Internet router and you can use other IP such as 192.168.1.123 if you like it more.), and set Gateway as 192.168.1.1 (this might be also different if you don't use 192.168.1.xxx as LAN address on your Internet router). Then, press "Submit" to restart 6lbr.
2. After restarting, you can check IP64 Address is 192.168.1.2 now on 6lbr Info page.
3. Next, let's check settings on Internet router (mine is Asus RT-N12HP_B1). We can see the external IP of this router is 126.96.36.199.
4.I add a port forwarding rule (assign http service port to 6lbr IPv4 address 192.168.1.2) to this Internet router and restart it.
5. Now, I can access 6lbr from another desktop from elsewhere on Internet by http://188.8.131.52