IPv6 Address Compression Practice

About this interactive

What you're seeing: a typed drill on IPv6 notation, run in both directions. Some items give you a full 128-bit address and ask for the compressed form; others give you a compressed address and ask for all eight hextets written out. Why it matters: compression is the one IPv6 skill you cannot look up mid-task — you read compressed addresses off router output and type expanded ones into configuration, and there is exactly one correct answer each way. Multiple choice lets you recognise a right answer; typing it is what proves you can produce one. The pool deliberately includes the three cases that trip people: an address with two zero runs of different lengths, where the double colon must take the longer one and the shorter one stays written out; an address whose two runs are the same length, where the double colon takes the leftmost and the other becomes 0:0; and an address with no all-zero hextet at all, where only the leading-zero rule applies. How to use it: work each blank on paper first — drop leading zeros, find the longest zero run, count that written hextets plus hidden hextets make eight — then type the result. Capital letters do not matter. Anything you miss shows the answer it wanted plus a hint carrying the full derivation, not just the value. Eight of the fifteen addresses are drawn each run, so running it twice gives you a different sheet.

What you'll learn

Compress a full 128-bit IPv6 address by suppressing the leading zeros within each hextet and replacing one run of all-zero hextets with the double colon
Choose which run of all-zero hextets the double colon replaces when an address contains more than one — the longest run, and the leftmost of two that tie — and explain why a second double colon is never permitted
Expand a compressed IPv6 address back to eight four-digit hextets by counting the written hextets to derive how many the double colon stands for, then restoring the omitted leading zeros
Distinguish a hextet that is entirely zeros, which the double colon can replace, from a hextet that merely contains zeros, which only the leading-zero rule touches
Verify a compressed or expanded result by confirming that the hextets written plus the hextets standing inside the double colon total eight

Aligned to

Cisco CCNA

1.8 Configure and verify IPv6 addressing and prefix

1.9 Describe IPv6 address types

Cisco CCST Networking

2.3 Identify IPv6 addresses and prefix formats

CompTIA Network+

3.4 Given a scenario, implement IPv4 and IPv6 network services

Key terms

IPv6: The sixth version of the Internet Protocol, using 128-bit addresses written in hexadecimal and separated by colons to provide a vastly larger address space than IPv4's 32-bit addresses. IPv6 also introduces built-in features like SLAAC, NDP, and mandatory support for IPsec.
Hextet: A group of four hexadecimal digits in an IPv6 address; eight hextets separated by colons form a complete 128-bit IPv6 address.
Double-Colon Notation: An IPv6 compression rule represented by '::' that replaces one or more consecutive all-zero 16-bit groups, usable only once per address.
Leading Zero Suppression: An IPv6 compression rule that allows leading zeros within any 16-bit group to be omitted.
Leading Zero: A zero that precedes the significant digits within a hextet of an IPv6 address, which may be suppressed in compressed notation and must be restored during expansion.
Link-Local Address: An IPv6 address in the FE80::/10 range that is automatically assigned to every IPv6-enabled interface and used only for communication within a single network link. It cannot be routed beyond the local Layer 2 segment and is required for Neighbor Discovery and router communication.

Topics

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