Applying Port Pre-Allocation and Incremental Allocation to the NAT444 Scenario
This section describes how to apply port pre-allocation and incremental allocation to the NAT444 scenario.
The carrier MAN is an IPv4 network. If too many users access the network, you can use port pre-allocation and incremental allocation to assign port ranges to the CPE in advance, reduce the log volume, and facilitate user address tracing.
Figure 1 shows the application of port pre-allocation and incremental allocation in the NAT444 scenario. In this scenario:
The CPE serves as a user access device to allocate private IPv4 addresses to users and perform level-1 NAT on service traffic.
The Broadband Remote Access Server (BRAS) functions as the access-layer device on the MAN. Generally having a built-in DHCP server module, the BRAS cooperates with the AAA server as a RADIUS client to implement CPE authentication and address allocation. In NAT444 scenarios, the BRAS allocates IPv4 addresses to CPEs. CPEs use these IPv4 addresses to communicate with the CGN device.
As the traffic convergence point, the CGN device needs to allocate public port ranges to CPE users and perform level-2 NAT on service traffic.
The syslog server interworking with the CGN device analyzes and resolves the logs from the CGN device to trace the addresses of the CPEs.
This feature is used to trace the IP addresses of CPEs, but not those of the users connected to the CPEs.
