I got sick of visually condensing networks to be put into routing tables, and couldn't find anything that would do this for me, so I threw together netsum, a small network summarizer tool.  It reads a list of prefixes via file or stdin, then spits out a condensed, or summarized, version.  For example…

Input:

10.80.226.0/24
10.80.226.1/24
10.80.10.0/25
172.16.1.91
50.50.50.50/32
172.16.1.90
66.85.192.2/24
66.85.193.20/24

Output:

10.80.10.0/25
10.80.226.0/24
50.50.50.50/32
66.85.192.0/23
172.16.1.90/31

Detects overlaps, sorts, and normalizes addresses, too.  And, urm, IPv6 support is coming soon.. yea.

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