Change the default local address range for IP from 1024 through 5000
to 20000 through 30000. These numbers are used for local IP port numbers
when an explicit address is not specified.

The values are sysctl modifiable under: net.inet.ip.port_{first|last}_auto

These numbers do not overlap with any known server addresses, without going
above 32768 which are "negative" on some other implementations.

20000 through 30000 is 2.5 times larger than the old range, but some have
suggested even that may not be enough... (gasp!) Setting a low address
of 10000 should be plenty.. :-)