Cisco Certified Support Technician (CCST) NetworkingNetworking FundamentalsHard
A network administrator needs to assign a static IPv6 address to a server. The network prefix is 2001:db8:abcd:0001::/64, and the server's MAC address is 00:1A:2B:3C:4D:5E. If using EUI-64 (Extended Unique Identifier-64) to generate the interface identifier, what would be the resulting IPv6 address?
- A2001:db8:abcd:0001:001A:2B:3C:4D5E
- B2001:db8:abcd:0001:021A:2BFF:FE3C:4D5E
- C2001:db8:abcd:0001:021A:2B3C:4D5E
- D2001:db8:abcd:0001:001A:2BFF:FE3C:4D5E
Show answer & explanationAnswer & explanation
Correct answer: B. 2001:db8:abcd:0001:021A:2BFF:FE3C:4D5E
To convert a MAC address to an EUI-64 interface identifier: 1. Split the MAC (00:1A:2B:3C:4D:5E) into two halves (00:1A:2B and 3C:4D:5E). 2. Insert 'FFFE' in the middle: 00:1A:2B:FF:FE:3C:4D:5E. 3. Invert the 7th bit of the first byte (00 becomes 02 in hex, since 00000000 becomes 00000010). The resulting EUI-64 is 021A:2BFF:FE3C:4D5E. Appending this to the /64 prefix gives 2001:db8:abcd:0001:021A:2BFF:FE3C:4D5E.
Why the other options are wrong
- A. This option incorrectly combines segments and misses the FFFE insertion and bit inversion.
- C. This option is missing the FFFE insertion and incorrectly combines parts.
- D. This option incorrectly keeps the first byte as 00 instead of inverting the 7th bit.
IPv6 EUI-64
A method used to automatically generate an IPv6 interface identifier (the last 64 bits of an IPv6 address) from a 48-bit MAC address, ensuring uniqueness for Stateless Address Autoconfiguration (SLAAC).
- Splits the 48-bit MAC address in half.
- Inserts the 16-bit value 'FFFE' in the middle.
- Inverts the 7th bit (universal/local bit) of the original MAC address's first octet.
Memory trick: MAC to EUI: Split, FFFE, Flip the 7th.