Convert the IPv6 address 0678:0DF5:0000:CB34:0034:0000:0000:02B0 to its most compressed form.

Convert the IPv6 address 0678:0DF5:0000:CB34:0034:0000:0000:02B0 to its most compressed form.

• A. 0678:DF5:0:CB34:34::2B0
• B. 678:DF5:0:CB34:34::2B0
• C. 678:DF5:0:CB34:34:0:0:2B0
• D. 678:DF5::CB34:34:0:2B0

Answer: (B)

IPv6 compression uses two rules: remove leading zeros in each hextet, and replace the longest run of consecutive zero hextets with a double colon, which can be used only once (and it must cover the longest such run). First, drop leading zeros in each part: 0678 becomes 678, 0DF5 becomes DF5, 0000 becomes 0, 0034 becomes 34, 0000 becomes 0, 0000 becomes 0, 02B0 becomes 2B0. This gives 678:DF5:0:CB34:34:0:0:2B0. Now identify zero runs. There are two consecutive zeros in a row near the end (after 34). That’s the longest run, so replace that pair with a double colon: 678:DF5:0:CB34:34::2B0. This is the proper compressed form, as it both removes leading zeros and uses the longest zero-run compression exactly once. The version with a leading zero left in the first hextet isn’t normalized, the version that doesn’t compress the zero run misses the opportunity to shorten, and a double colon replacing a single zero wouldn’t be valid.

IPv6 compression uses two rules: remove leading zeros in each hextet, and replace the longest run of consecutive zero hextets with a double colon, which can be used only once (and it must cover the longest such run).

First, drop leading zeros in each part: 0678 becomes 678, 0DF5 becomes DF5, 0000 becomes 0, 0034 becomes 34, 0000 becomes 0, 0000 becomes 0, 02B0 becomes 2B0. This gives 678:DF5:0:CB34:34:0:0:2B0.

Now identify zero runs. There are two consecutive zeros in a row near the end (after 34). That’s the longest run, so replace that pair with a double colon: 678:DF5:0:CB34:34::2B0.

This is the proper compressed form, as it both removes leading zeros and uses the longest zero-run compression exactly once. The version with a leading zero left in the first hextet isn’t normalized, the version that doesn’t compress the zero run misses the opportunity to shorten, and a double colon replacing a single zero wouldn’t be valid.