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Secured Port Block Allocation for Port Translation

You can configure secured port block allocation, which allocates blocks of ports to a subscriber for source NAT port translation. The most recently allocated block is the current active block. New requests for NAT ports for the subscriber are served from the active block. Ports are allocated randomly from the current active block.

Carriers track subscribers using the IP address (RADIUS or DHCP) log. If they use port translation without port block allocation, an IP address is shared by multiple subscribers, and the carrier must track the IP address and port, which are part of the NAT log. Because ports are used and reused at a very high rate, tracking subscribers using the log becomes difficult because of the large number of messages, which are difficult to archive and correlate. By using port block allocation, you can significantly reduce the number of logs, making it easier to track subscribers.

With port block allocation, we generate one syslog log per set of ports allocated for a subscriber. These logs are UDP based and can be lost in the network, particularly for long-running flows. You can configure an interim logging interval to re-send logs for active blocks that have traffic on at least one of the ports.