Configuring IPv6 RA


  1. Enable transmission of IPv6 router advertisements with the command no ipv6 nd suppress-ra.
  2. Optionally, configure IPv6 unicast address prefixes with the command ipv6 nd prefix.
  3. Optionally, configure support for DNS name resolution with the commands ipv6 nd ra dns server and ipv6 nd ra dns search-list.
  4. For most deployments, the default values for the following features do not need to be changed. If your deployment requires different settings, change the default values with the indicated command:

    IPv6 RA setting

    Default value

    Command to change it

    Number of neighbor solicitations to be sent when performing DAD.


    ipv6 nd dad attempts

    Number of neighbor entries in the ND cache.


    ipv6 nd cache-limit

    Hop limit to be sent in the RA messages.


    ipv6 nd hop-limit

    MTU value to be sent in the RA messages.

    1500 bytes

    ipv6 nd mtu

    Neighbor solicitation interval

    1000 milliseconds

    ipv6 nd ns-interval

    Lifetime of a default router.

    1800 seconds

    ipv6 nd ra lifetime

    Retrieval of an IPv6 address by devices.


    ipv6 nd ra managed-config-flag

    Maximum interval between transmissions of IPv6 RAs.

    600 seconds

    ipv6 nd ra max-interval

    Minimum interval between transmissions of IPv6 RAs.

    200 seconds

    ipv6 nd ra min-interval

    Time that an interface considers a device to be reachable.

    0 milliseconds (no limit)

    ipv6 nd ra reachable-time

    Retry period between ND solicitations.

    0 (Use locally configured NS-interval)

    ipv6 nd ra retrans-timer

    Default routing preference for an interface.


    ipv6 nd router-preference

  5. Review IPv6 RA configuration settings with the commands show ipv6 nd interface, show ipv6 nd interface prefix, show ipv6 nd ra dns server, and show ipv6 nd ra dns search-list.


This example creates the following configuration:

  • Enables IPV6 RA on interface 1/1/3.
  • Sets the recursive DNS server address to 4001::1 with a lifetime of 400 seconds.
  • Sets the minimum interval between transmissions to 3 seconds.
  • Sets the maximum interval between transmissions to 13 seconds.
  • Sets the lifetime of a default router to 1900 seconds.
switch(config)# interface 1/1/3 switch(config-if)# no ipv6 nd suppress-ra switch(config-if)# ipv6 nd ra dns server 4001::1 lifetime 400 switch(config-if)# ipv6 nd ra min-interval 3 switch(config-if)# ipv6 nd ra max-interval 13 switch(config-if)# ipv6 nd ra lifetime 1900 switch(config-if)# end switch# show ipv6 nd interface 1/1/3 Interface 1/1/3 is up Admin state is up IPv6 address: 2006::1/64 [VALID] IPv6 link-local address: fe80::98f2:b321:368:6dc6/64 [VALID] ICMPv6 active timers: Last Router-Advertisement sent: 0 Secs Next Router-Advertisement sent in: 13 Secs Router-Advertisement parameters: Periodic interval: 3 to 13 secs Router Preference: medium Send "Managed Address Configuration" flag: false Send "Other Stateful Configuration" flag: false Send "Current Hop Limit" field: 64 Send "MTU" option value: 1500 Send "Router Lifetime" field: 1900 Send "Reachable Time" field: 0 Send "Retrans Timer" field: 0 Suppress RA: false Suppress MTU in RA: true ICMPv6 error message parameters: Send redirects: false ICMPv6 DAD parameters: Current DAD attempt: 1 switch# show ipv6 nd ra dns server Recursive DNS Server List on: 1/1/3 Suppress DNS Server List: No DNS Server 1: 2001::1 lifetime 400