ipv6 nd nud reachable-time

Usage Scenario

Setting the IPv6 neighbor reachable time provides the following functions:

• Controlling the aging time of neighbor entries on a local routing device.

• Being a parameter in an RA packet to enable a host to configure the neighbor reachable time.

Each RA packet sent by a routing device carries the neighbor reachable time. This allows all nodes along the same link to use the same neighbor reachable time.

Prerequisites

The IPv6 function has been enabled on the interface using the ipv6 enable command in the interface view.

Precautions

A shorter neighbor reachable time enables a routing device to detect neighbor reachability more quickly. However, this consumes more network bandwidth and CPU resources. Therefore, a short neighbor reachable time is not recommended on an IPv6 network. The default value, 30000 ms, is recommended.

If you run the ipv6 nd nud reachable-time command multiple times, only the latest configuration takes effect.

The neighbor reachable time set on a routing device is the same as that carried in an RA packet. In the following cases, however, the neighbor reachable time set on a routing device is the default value 30000 ms while the neighbor reachable time carried in the RA packet is 0 millisecond:

• No neighbor reachable time is set on the routing device. The default value takes effect.
• The undo ipv6 nd nud reachable-time command is run to restore the neighbor reachable time to the default value.

After a host receives an RA packet in which the neighbor reachable time is 0 ms, the host sets the neighbor reachable time to 30000 ms, the same as that on the device.