Cisco Certified Network Associate (CCNA) 2026 – 400 Free Practice Questions to Pass the Exam

In IPv6 addressing, the structure and formatting of the addresses are crucial for them to be valid. The correct choice adheres to the established rules for IPv6 addresses.

The address that is valid must consist of eight groups of four hexadecimal digits, separated by colons. It can also utilize the double colon (::) to represent contiguous blocks of zeros, but this can only appear once in an address. The address "2004:1:25A4:886F::1" correctly follows these guidelines. It features a mix of groups with valid hexadecimal digits, including the use of a double colon to compress the address, which is appropriate since it indicates the omission of the necessary leading zeros for one group.

The other choices present invalid formats for various reasons. One contains the letter 'W', which is not a valid hexadecimal character. Others either have an improper amount of colons or do not conform to the hexadecimal character requirements, making them invalid according to the IPv6 specifications. Therefore, "2004:1:25A4:886F::1" stands out as the only valid IPv6 address in this context.