You're right to subtract both the first and last addresses that fall under the mask, but if the input contains an explicit broadcast address like the OP says it's better to stick with that for output; I believe some old equipment uses 0 instead of -1 for broadcast.

(And your regexp works, but "\." is a bit better than ".".)

Nifty implementation though.

In reply to Re^3: algorithm for network address enumeration by gaal
in thread algorithm for network address enumeration by knave

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