Learn CIDR
CIDR blocks contain aligned powers of two addresses. Increasing prefix length halves block size.
Read each short explanation, work through the example, then answer a pop quiz. Every answer explains the reasoning. Incorrect answers unlock a fresh question on the same idea; the full lesson contains ten questions.
01Understand the basics
Ready to learnClassless Inter-Domain Routing (CIDR) writes an address block as a network address and prefix length. Blocks must begin on a boundary that matches their size. A summary route should cover exactly the intended networks unless extra coverage is deliberate.
02Split a block
Ready to learnEach extra prefix bit splits a block into two equal children. The address space stays the same; only the boundaries change.
Try a different value
03Summarise without adding routes
Ready to learnAdjacency alone is not enough for an exact merge: the larger block also needs an aligned starting address. Check the full resulting range before advertising a summary.
You’ve practised all three sections.
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