IPv6Interface Config

ipv6 enable

Enables IPv6 processing on an interface, allowing the interface to forward IPv6 traffic and participate in IPv6 routing protocols.

Syntax·Interface Config

ipv6 enable

When to Use This Command

Enable IPv6 on a router interface connected to an IPv6-enabled network segment.
Prepare an interface for IPv6 static routing or dynamic routing protocols like OSPFv3 or EIGRP for IPv6.
Allow a router interface to send and receive IPv6 Router Advertisements for SLAAC.
Enable IPv6 on a VLAN interface for inter-VLAN routing with IPv6.

Command Examples

Enable IPv6 on a GigabitEthernet interface

interface GigabitEthernet0/0
 ipv6 enable

Router(config-if)# ipv6 enable
Router(config-if)# end
Router# show ipv6 interface brief
GigabitEthernet0/0   [up/up]
    FE80::1
    2001:DB8:1::1

The command enables IPv6 on the interface. The 'show ipv6 interface brief' output confirms the interface is up/up and shows the link-local address (FE80::1) and the global unicast address (2001:DB8:1::1) if configured.

Enable IPv6 on a Serial interface for point-to-point link

interface Serial0/0/0
 ipv6 enable

Router(config-if)# ipv6 enable
Router(config-if)# end
Router# show ipv6 interface serial0/0/0
Serial0/0/0 is up, line protocol is up
  IPv6 is enabled, link-local address is FE80::2
  No global unicast address is configured
  Joined group address(es):
    FF02::1
    FF02::2
    FF02::1:FF00:2
  MTU is 1500 bytes

The output shows that IPv6 is enabled with a link-local address (FE80::2) but no global address. The joined group addresses indicate multicast groups for all-nodes (FF02::1), all-routers (FF02::2), and solicited-node (FF02::1:FF00:2).

Understanding the Output

The 'show ipv6 interface' command provides detailed IPv6 status. Key fields: 'IPv6 is enabled' confirms the command worked; 'link-local address' is automatically generated (FE80::/10); 'No global unicast address' means you need to assign one with 'ipv6 address'. 'Joined group address(es)' shows multicast groups the interface listens to. 'MTU' is the maximum transmission unit. In a real network, ensure the interface is up/up and has a global address for routing. Watch for 'IPv6 is disabled' if the command wasn't applied, or 'Tentative' if DAD is in progress.

CCNA Exam Tips

CCNA exam tip: 'ipv6 enable' is required before assigning an IPv6 address or using IPv6 routing protocols on an interface.

CCNA exam tip: The command automatically generates a link-local address using EUI-64; you can override it with 'ipv6 address link-local'.

CCNA exam tip: Without 'ipv6 enable', the interface will not process IPv6 traffic even if an IPv6 address is configured (though some IOS versions auto-enable).

CCNA exam tip: On exam simlets, remember to enter interface configuration mode first, then apply 'ipv6 enable'.

Common Mistakes

Mistake 1: Forgetting to enter interface configuration mode before typing 'ipv6 enable', resulting in '% Invalid input detected'.

Mistake 2: Assuming 'ipv6 enable' also assigns a global unicast address; it only enables IPv6 and creates a link-local address.

Mistake 3: Using 'ipv6 enable' on a switch port that is not a routed port (SVI or no switchport); on Layer 2 ports, use 'ipv6 enable' only on SVIs.

Related Commands

ipv6 address [prefix/len]

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

ipv6 unicast-routing

Enables IPv6 unicast routing on a Cisco router, allowing it to forward IPv6 packets and participate in IPv6 routing protocols.

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