Cisco CCNA mock exam questions sample test – Question 55

.Which of the following commands will enable a global IPv6 address based on the Modified EUI-64 format interface ID?

A. ipv6 address 5000::2222:1/64
B. ipv6 address autoconfig
C. ipv6 address 2001:db8:2222:7272::72/64 link-local
D. ipv6 enable

Correct Answer: B

To configure the interface to create a global IPv6 address based on the Modified EUI-64 format interface ID, you must enable stateless autoconfiguration. In stateless autoconfiguration, the interface will receive the network prefix from the router advertisement (RA) and generate a full IPv6 address by spreading the 48-bit MAC address of the interface across 64 bits to complete the address. This can all be done simply by executing the ipv6 address autoconfig command at the interface configuration prompt.
The command ipv6 address 5000::2222:1/64 is used to manually assign a full IPv6 address to the interface without using stateless autoconfiguration or the eui-64 keyword to manually specify the first 64 bits and allow the last 64 bits to be generated from the MAC address of the interface.
The command ipv6 address 2001:db8:2222:7272::72/64 link local is used to configure a link-local address manually without allowing the system to generate one from the MAC address, which is the default method.
The command ipv6 enable is used to allow the system to generate a link-local address from the MAC address. Because this is the default behavior, the command is not required if any other ipv6 commands have been issued. Regardless of how many manual IPv6 addresses you configure, a link local address is always generated by default.

Network Fundamentals
Configure, verify, and troubleshoot IPv6 addressing
Cisco > Product Support > Security > Cisco ASA 5500-X Series Firewalls > Configure > Configuration Guides > Cisco Security Appliance Command Line Configuration Guide, Version
7.2 > Chapter: Configuring IPv6 > Enforcing the Use of Modified EUI-64 Interface IDs in IPv6 Addresses
Cisco > Support > Cisco IOS IPv6 Command Reference > ipv6 address