We discussed some of the possible scenarios for CGNAT implementation. Why telco chose this is probably due to the lack of IPv4 address.
Here is a screen shot we took showing the 100.73.x.y IP address issued to my PC which is directly connected to the ONT.
If you were to connect to a router, the IP address will be the WAN IP. The difference is that if it was a public IP address like 203.1.2.100, you can use a dynamic dns to map it to a URL e.g. username.dyndns.org. At your router end you can enable port forwarding to access certain hosted servers or your NAS.
With the private IP of 100.73.x.y, there is a difficulty to host your own servers at home. If you try to access the addr 203.1.2.100 from outside the network, which machine will it be referring to as it is shared by multiple users.
There are work around but you may need some technical know how to cross the hurdle. If SIMBA offers a VAS for a fixed ipv4 addr, things will be simplier for those who wish to do so.
Anyway, if you are like 99% who don’t need to host a server at home, CGNAT is basically transparent to the end user and it won’t affect your daily surfing or streaming of videos. Do check out our review of the SIMBA Fibre Broadband at this link.