need an algorithm for collapsing netblock ranges into lists of superset ranges

Question

My math-fu is failing me! I need an efficient way of reducing network ranges to supersets, e.g. if I input list of IP ranges:

• 1.1.1.1 to 2.2.2.5
• 1.1.1

Answer 1

Alright, my coworker came up with this answer, which I think is pretty excellent. Let me know if you see any issues:

• Order the IP ranges by StartingIP
• For each row "x" to insert:
  • If there is a previous row "y" in the list, fetch:
    • If x and y are contiguous, extend y to x's EndingIP
    • Else if x.StartingIP <= y.StartingIP and x.EndingIP > y.EndingIP, extend y to x.EndingIP
    • Else if x is a subset of y, do nothing
    • Else, create a new range
  • Else, create a new range and insert into the list