External carrier-grade NAT (CGNAT) with RADIUS accounting support for subscribers

You can enable the external carrier-grade NAT feature on a broadband network gateway (BNG) router. With this configuration, you can offload Network Address Translation (NAT) and Network Address Port Translation (NAPT) functions to a dedicated carrier-grade NAT device while retaining subscriber management functions on the BNG router. Use the external-napt statement to enable external carrier-grade NAT on the BNG router. You can also manage external carrier-grade NAT through the RADIUS server by using the predefined variable $junos-external-napt-control.

When you enable external carrier-grade NAT and accounting services, the BNG records public IP address and public port block information received from the carrier-grade NAT device through RADIUS vendor-specific attribute (VSA) 238.