200-301 · Question #1115
Refer to the exhibit. The iPv6 address for the LAN segment on router R2 must be configured using the EUI-64 format. Which address must be used?
The correct answer is A. ipv6 address 2001:DB8:D8D2:1009:10A0:ABFF:FECC:1 eui-64. Configuring an IPv6 address with EUI-64 involves deriving the interface identifier from the interface's MAC address by splitting it, inserting FFFE, and inverting the 7th bit of the first byte.
Question
Refer to the exhibit. The iPv6 address for the LAN segment on router R2 must be configured using the EUI-64 format. Which address must be used?
Exhibits
Options
- Aipv6 address 2001:DB8:D8D2:1009:10A0:ABFF:FECC:1 eui-64
- Bipv6 address 2001:DB8:D8D2:1009:1230:ABFF:FECC:1 eui-64
- Cipv6 address 2001:DB8:D8D2:1009:4331:89FF:FF23:9 eui-64
- Dipv6 address 2001:DB8:D8D2:1009:12A0:AB34:FFCC:1 eui-64
How the community answered
(53 responses)- A75% (40)
- B8% (4)
- C2% (1)
- D15% (8)
Why each option
Configuring an IPv6 address with EUI-64 involves deriving the interface identifier from the interface's MAC address by splitting it, inserting FFFE, and inverting the 7th bit of the first byte.
R2's GigabitEthernet0/0/1 MAC address is 12A0.ABCC.0001. EUI-64 conversion splits the MAC into 12A0.AB and CC.0001, inserts FFFE to get 12A0:ABFF:FECC:0001. Inverting the 7th bit of the first byte (12h, or 00010010b) changes it to 10h (00010000b). Thus, the interface ID is 10A0:ABFF:FECC:0001, combined with the prefix 2001:DB8:D8D2:1009::/64, forms 2001:DB8:D8D2:1009:10A0:ABFF:FECC:1 eui-64.
This option's interface identifier (1230:ABFF:FECC:1) does not correctly result from the EUI-64 conversion of the given MAC address, specifically the first hextet is incorrect.
This option uses incorrect segments (e.g., 89FF:FF23) that do not correspond to the EUI-64 conversion rules from the specified MAC address, and is missing the FFFE insertion in the correct position.
This option fails to correctly invert the 7th bit of the MAC address's first byte, retaining '12A0' instead of '10A0', and also contains an incorrect segment 'AB34' instead of 'ABFF'.
Concept tested: IPv6 Modified EUI-64 address generation with `eui-64` command
Source: https://www.cisco.com/c/en/us/td/docs/ios/ipv6/configuration/guide/ipv6_address_config_c_ipv6-address-cfg-book/ipv6_address_config_c_ipv6-address-cfg-book_chapter_010.html
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