Dell EMC SmartFabric OS10 User Guide Release 10.5.0

Neighbor Discovery

The IPv6 NDP determines if neighboring IPv6 devices are reachable and receives the IPv6 addresses of IPv6 devices on local links. Using the link-layer and global prefixes of neighbor addresses, OS10 performs stateless autoconfiguration of IPv6 addresses on interfaces.

ICMPv6 RA messages advertise the IPv6 addresses of IPv6-enabled interfaces and allow a router to learn of any address changes in IPv6 neighbors. By default, RAs are disabled on an interface.

Prerequisites

To enable RA messages, the switch must be in Router mode with IPv6 forwarding enabled and stateless autoconfiguration disabled using the no ipv6 address autoconfig command.

Enable router advertisement messages

1. Enable IPv6 neighbor discovery and sending ICMPv6 RA messages in Interface mode.

   ipv6 nd send-ra

2. (Optional) Configure IPv6 neighbor discovery options in Interface mode.
   • ipv6 nd hop-limit hops — (Optional) Sets the hop limit advertised in RA messages and included in IPv6 data packets sent by the router, from 0 to 255; default 64. 0 indicates that no hop limit is specified by the router.
   • ipv6 nd managed-config-flag — (Optional) Sent in RA messages to tell hosts to use stateful address autoconfiguration, such as DHCPv6, to obtain IPv6 addresses.
   • ipv6 nd max-ra-interval seconds — (Optional) Sets the maximum time interval for sending RA messages, from 4 to 1800 seconds; default 600.
   • ipv6 nd mtu number — (Optional) Sets the maximum transmission unit (MTU) used in RA messages on the link, from 1280 to 65535 bytes; default 1500. By default, no MTU setting is included in RA messages.
   • ipv6 nd other-config-flag — (Optional) Tells hosts to use stateful autoconfiguration to obtain nonaddress-related information.
   • ipv6 nd ra-lifetime seconds — (Optional) Sets the lifetime of a default router in RA messages, from 0 to 9000 milliseconds; default 3 times the max-ra-interval setting. 0 indicates that this router is not used as a default router.
   • ipv6 nd reachable-time milliseconds — (Optional) Sets the advertised time the router sees that a neighbor is up after it receives neighbor reachability confirmation, from 0 to 3600000 milliseconds; default 0. 0 indicates that no reachable time is sent in RA messages.
   • ipv6 nd retrans-timer seconds — (Optional) Sets the time between retransmitting neighbor solicitation messages, from 100 to 4292967295 milliseconds. By default, no retransmit timer is configured.
3. Configure the IPv6 prefixes that are advertised by IPv6 neighbor discovery in Interface mode.

   ipv6 nd prefix {ipv6-prefix | default} [no-advertise] [no-autoconfig] [no-rtr-address] 
   [off-link] [lifetime {valid-lifetime seconds | infinite} 
   {preferred-lifetime seconds | infinite}]

   • ipv6-prefix — Enter an IPv6 prefix in x:x::y/mask format to include the prefix in RA mesages. Include prefixes that are not already in the subnets configured on the interface.
   • default — Configure the prefix parameters advertised in all subnets configured on the interface.
   • no-advertise — (Optional) Do not advertise the specified prefix. By default, all prefixes in configured subnets are advertised.
   • no-autoconfig — (Optional) Sets AdvAutonomous to Off for the specified prefix in the radvd.conf file. This setting tells hosts to not use this prefix for address autoconfiguration. By default, AdvAutonomous is On.
   • no-rtr-address — (Optional) Sets AdvRouterAddr to Off for the prefix in the radvd.conf file. The Off setting tells hosts to not use the advertising router address for on-link determination. By default, AdvRouterAddr is On.
   • off-link — (Optional) Sets AdvOnLink to Off for the prefix in the radvd.conf file. The Off setting tells hosts to not use this prefix for on-link determination. By default, AdvOnLink is On.
   • lifetime {valid-lifetime seconds | infinite} — (Optional) Sets AdvValidLifetime in seconds for the prefix in the radvd.conf file. The prefix is valid for on-link determination only for the specified lifetime. The default is 86400 seconds (1 day). The infinite setting allows the prefix to be valid for on-link determination with no time limit.
   • lifetime {preferred-lifetime seconds | infinite} — (Optional) Sets AdvPreferredLifetime in seconds for the prefix in the radvd.conf file. IPv6 addresses generated from the prefix using stateless autoconfiguration remain preferred for the configured lifetime. The default is 14400 seconds (4 hours). The infinite setting allows addresses that are autoconfigured using the prefix to be preferred with no time limit.

   By default, all prefixes configured in IPv6 addresses on an interface are advertised. To modify the default values advertised for interface subnet prefixes, use the ipv6 nd prefix default command and specify new default settings.

   On-link determination is the process used to forward IPv6 packets to a destination IPv6 address.

Configure neighbor discovery

OS10(config)# interface ethernet 1/1/1
OS10(conf-if-eth1/1/1)# ipv6 nd mtu 1500
OS10(conf-if-eth1/1/1)# ipv6 nd send-ra

Configure advertised IPv6 prefixes

OS10(config)# interface ethernet 1/1/1
OS10(conf-if-eth1/1/1)# ipv6 nd prefix default lifetime infinite infinite
OS10(conf-if-eth1/1/1)# ipv6 nd prefix 2002::/64