Configuring Neighbor Discovery
Context
IPv6 NDP provides address resolution, neighbor unreachability detection, DAD, router/prefix discovery, address autoconfiguration, and redirection.
After the IPv6 function is enabled on the router, the router automatically implements address resolution, DAD, and redirection. Neighbor unreachability detection, router/prefix discovery, and address autoconfiguration need to be manually configured. You can also configure the router to send RA packets to enable router/prefix discovery and address autoconfiguration, and enable the automatic detection of ND entries to check whether neighbors are reachable.
After the automatic detection of ND entries is enabled on the router, the router can send NS packets to check whether neighbors are reachable before aging ND entries. If neighbors are reachable, the router updates ND entries; otherwise, the router ages ND entries.
You can enable the router to send RA packets. After receiving the RA packets, network nodes perform address autoconfiguration and router/prefix discovery based on the prefix and other configuration information contained in RA packets.
After the preceding configurations are complete, NDP functions work properly. You can also adjust ND parameters based on service requirements.
Procedure
- Run the following commands to enable NDP functions to work properly.
Run system-view
The system view is displayed.
Run interface interface-type interface-number
The specified interface view is displayed.
Run undo ipv6 nd ra halt
The system is enabled to send RA packets.
By default, the system is disabled from sending RA packets.
To configure neighbor discovery on a subinterface, you need to run the ipv6 nd ns multicast-enable command to enable the subinterface to send NS multicast packets.
- (Optional) After completing the preceding steps, adjust ND parameters to meet service requirements.
Run the following commands in the system view.
Run quit
Return to the system view.
In the system view, run: ipv6 nd hop-limit limit
The hop limit for IPv6 unicast packets initially sent by a device is set.
By default, the IPv6 unicast packets initially sent by a device can travel a maximum of 64 hops.
In the system view, run: ipv6 nd stale-timeout timeout-value
The aging time of ND entries in STALE state is set.
By default, the aging time of ND entries in STALE state is 1200 seconds.
Run the following commands on the interface.
Run interface interface-type interface-number
The specified interface view is displayed.
Run ipv6 nd stale-timeout timeout-value
The aging time of ND entries in STALE state is set.
By default, the aging time of ND entries in STALE state is not set on interfaces and is the same as the aging time set in the system view.
Run ipv6 nd ns retrans-timer interval
The interval for sending NS packets is set.
By default, the interval for sending NS packets is 1000 ms.
Run ipv6 nd ra { max-interval maximum-interval | min-interval minimum-interval }
The interval for sending RA packets is set.
By default, the maximum interval is 600s and the minimum interval is 200s.
(Optional) Run ipv6 nd ra prefix default no-advertise
RA messages are configured not to carry the default prefix generated based on the interface IPv6 address.
By default, RA messages carry the default prefix generated based on the interface IPv6 address.
Run ipv6 nd ra prefix ipv6-address prefix-length valid-lifetime preferred-lifetime [ no-autoconfig ] [ off-link ]
Prefix information in RA packets is configured.
By default, the prefix in RA packets is the network prefix of the link where the interface sending RA packets resides.
Prefixes configured using the ipv6 nd ra prefix command take precedence over the default prefix generated based on the interface IPv6 address. An RA packet can carry a maximum of 10 prefixes. If exactly 10 prefixes are configured manually, the default prefix is not used.
Run ipv6 nd autoconfig managed-address-flag
The managed address configuration flag (M flag) for stateful autoconfiguration in RA packets is set.
By default, the M flag in an RA packet is not set.
Run ipv6 nd autoconfig other-flag
The other configuration flag (O flag) for stateful autoconfiguration in RA packets is set.
By default, the O flag in an RA packet is not set.
Run ipv6 nd nud reachable-time value
The IPv6 neighbor reachable time is set.
By default, the IPv6 neighbor reachable time is 1200000 ms.
Run ipv6 nd ra router-lifetime ra-lifetime
The time to live (TTL) is set for RA packets.
By default, the TTL of RA packets is 1800s.
Run ipv6 nd ra preference { high | medium | low }
The priority of the default router in RA packets is set.
Run ipv6 nd ra route-information ipv6-address prefix-length lifetime route-lifetime [ preference { high | medium | low } ]
Route option information in RA packets is set.
Run ipv6 nd dad attempts value
The number of times NS packets are sent when the system performs DAD is set.
By default, the number of times NS packets are sent when the system performs DAD is 1.