I believe this thread should move to Airtel from here. Don't know who is the moderator here
@drtech
Here is the (long) explanation...
Current implementation for static IPs at Airtel needs you to go away from PPPoE and they will provide you a dedicated /30 address for WAN which you need to configure on your WAN
router with a default route (0.0.0.0/0) pointing towards the other IP in the /30 pool.
At the same time they will provision the other IP in that /30 on the your port/VLAN of their Broadband Gateway. For the /28 or /29 pool which you pay for, they will put a route on their Broadband Router towards your /30 IP so that traffic coming from Internet destined to one of the IPs in that /28 range reaches your router. There is no NAT here as the IP in that LAN pool are public IP addresses which are routable over the Internet. Needless to say that bunch of smaller LAN pools (from yours and other customers) are aggregated as /24 or larger when advertised to Internet as you cant route smaller that /24 subnet over internet.
The NAT happens in the residential PPPoE scenario where your device behind your WAN router gets IP from 192.168.x.x range or any other private IP range.
Another important point is that there is no authentication for this unlike the way you have a user/password in the PPPoE connection
Hope that is clear
As far as pricing is concerned, I am not aware of that. Please contact CC for that.
IMO this is a bad implementation as we waste lots of IPs here...