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Jbz
Jun 6, 2011

Huge idiot here, I'm taking the ICND1 in a couple weeks and doing practice exams. Came across this question and I can't figure out why the /17 is the Most Correct answer.

Explanation says: "Of the routes for the 100.100.0.0 network shown, three of them would match for the 100.100.100.50 destination: 100.100.0.0/14, 100.100.0.0/16, and 100.100.0.0/17. The 100.100.0.0/21 route would not match the 100.100.100.50 destination because it would include only the addresses from 100.100.0.0 through 100.100.7.255, inclusively."

Re-reading the relevant chapter from the book wasn't helpful.

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Jbz
Jun 6, 2011

Methanar posted:

If a destination matches multiple routes, it will take the most specific one.

https://en.wikipedia.org/wiki/Longest_prefix_match

This is actually how 0.0.0.0/0 works.

It's the least specific route possible, it will always match if nothing else does. Its not just a hardcoded magic number, its logically consistent with all other routes.

Thank you very much. As expected I'm just a dumbdumb.

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