ip_local_port_range

Defines the local port range that is used by TCP and UDP to choose the local port. The first number is the first, the second the last local port number. The default value depends on the amount of memory available on the system: > 128MB 32768 - 61000, < 128MB 1024 - 4999 or even less.

This number defines number of active connections, which this system can issue simultaneously to systems not supporting TCP extensions (timestamps). With tcp_tw_recycle enabled, range 1024 - 4999 is enough to issue up to 2000 connections per second to systems supporting timestamps.