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. 1 ipv6 nd dad attempts
    Number of neighbor entries in the ND cache. 131072 ipv6 nd cache-limit
    Hop limit to be sent in the RA messages. 64 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. Disabled 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. Medium 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)# 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