IPv6Interface Config

ipv6 address [addr] link-local

Assigns a link-local IPv6 address to an interface, overriding the automatically generated EUI-64 address.

Syntax·Interface Config

ipv6 address [addr] link-local

When to Use This Command

Manually specifying a well-known link-local address for easier troubleshooting (e.g., FE80::1 on a router interface).
Ensuring consistent link-local addressing across redundant links for predictable OSPFv3 or EIGRPv6 neighbor relationships.
Configuring a specific link-local address for security or policy-based routing purposes.
Avoiding automatic EUI-64 generation when interface MAC changes (e.g., on redundant supervisor modules).

Command Examples

Assign a specific link-local address

ipv6 address fe80::1 link-local

Router(config-if)# ipv6 address fe80::1 link-local
Router(config-if)# end
Router# show ipv6 interface brief
GigabitEthernet0/0   [up/up]
    FE80::1
    unassigned

The command assigns FE80::1 as the link-local address. 'show ipv6 interface brief' confirms the link-local address is now FE80::1 instead of the auto-generated EUI-64 address.

Override auto-generated link-local address

ipv6 address fe80::2 link-local

Router(config-if)# ipv6 address fe80::2 link-local
% Interface GigabitEthernet0/0 already has a link-local address FE80::2E0:FCFF:FE00:1
% Overwriting with FE80::2
Router(config-if)# end
Router# show ipv6 interface gigabitethernet 0/0 | include link-local
  IPv6 is enabled, link-local address is FE80::2

The warning indicates an existing link-local address is being replaced. The 'show ipv6 interface' output confirms the new link-local address.

Understanding the Output

The command itself produces no output unless there is a conflict. Use 'show ipv6 interface [interface]' or 'show ipv6 interface brief' to verify. In 'show ipv6 interface', look for 'link-local address is' followed by the address. A manually configured link-local address will appear exactly as configured; an auto-generated one will include the EUI-64 format (e.g., FE80::2E0:FCFF:FE00:1). Ensure the address is in the FE80::/10 range; otherwise, the command will be rejected.

CCNA Exam Tips

CCNA 200-301: Remember that link-local addresses must be in the FE80::/10 range; any other prefix will be rejected.

CCNA 200-301: The 'link-local' keyword is mandatory; omitting it assigns a global unicast address instead.

CCNA 200-301: Manually configured link-local addresses override auto-generated ones; this is a common exam scenario.

CCNA 200-301: Use 'show ipv6 interface brief' to quickly verify link-local addresses on all interfaces.

Common Mistakes

Forgetting the 'link-local' keyword, which assigns a global unicast address instead of a link-local address.

Using an address outside the FE80::/10 range, causing the command to be rejected.

Assuming the link-local address is automatically derived from the MAC address; manual configuration overrides it.

Related Commands

ipv6 address [prefix/len]

Assigns a global unicast or link-local IPv6 address to an interface, enabling IPv6 routing on that interface.

show ipv6 interface brief

Displays a summary of IPv6 interface status and addresses, useful for quickly verifying IPv6 configuration and interface operational state.

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