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Computer Networks · Problem type
Longest-prefix match
Use this for “A router has 10.1.2.0/24, 10.1.0.0/16, 10.0.0.0/8 and a default route. Where does 10.1.9.9 go?”
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Which forwarding-table entry does the router use for this address?
Tap a card, then tap its group.
Here every prefix ends on a dot, so /8, /16 and /24 compare the first one, two or three numbers of the address.
Assumptions
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An address matches an entry when its first n bits equal the entry’s first n bits (/n).
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Of all the entries that match, the router uses the one with the longest prefix.
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The default route, 0.0.0.0/0, matches every address, so it is used only when nothing else does.
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