(Optional) Configuring User Status Detection

Context

After ND snooping is configured, a device creates entries in the dynamic ND snooping binding table by checking NS packets and updates entries in the dynamic ND snooping binding table by checking NS or NA packets. The aging time of a dynamic ND snooping binding entry depends on the corresponding user's IPv6 address lease time. If the address lease time does not expire but the user is offline, the dynamic ND snooping binding entry corresponding to the user cannot be deleted, which occupies binding entry resources on the device and causes a failure in updating entry information.

To solve this problem, you can configure user status detection. The detection methods include periodic detection and detection triggered by an NA packet with an IP address the same as that in the entry and a port number different from that in the entry.

Periodic detection:

After periodic detection is enabled, the device sends NS packets to the user based on the detection times (n) and interval configured using the nd user-bind detect command. If the device does not receive an NA packet from the user after sending a specified number of NS packets, the device considers the user to be offline and deletes the dynamic ND snooping binding entry corresponding to the user.

On a small network with good network quality, the user returns an NA packet quickly. In this case, you can set the interval for sending NS packets to a smaller value. On a large network with poor network quality, the user returns an NA packet slowly. You can set the interval for sending NS packets to a larger value to prevent the device from sending another NS packet before receiving the NA packet. You can change the interval based on the actual network environment.
Detection triggered by a conflicting NA packet:
If the device receives an NA packet with the IP address the same as that in the corresponding entry and inbound port number different from that in the entry, the NA packet conflicts with the entry. The device is then triggered to send an NS packet to detect whether the user corresponding to the entry is online.
- If the entry is within the lifetime and the device receives an NA packet from the port corresponding to the entry, the user corresponding to the entry is still online and the device updates the IP address lease in the corresponding entry.
- If the entry is within the lifetime and the device does not receive an NA packet from the port corresponding to the entry, the user corresponding to the entry is offline and the device updates the user's IP address lease time in the entry and updates the port number in the entry to that in the previously received NA packet.

After the device receives an NA packet conflicting with an ND snooping binding entry and user status detection is enabled, periodic user status detection is suspended.

Procedure

Periodic detection:
1. Run system-view
  The system view is displayed.
2. Run nd user-bind detect enable
  
  The function of periodically detecting status of users corresponding to dynamic ND snooping binding entries is enabled.
  
  By default, the function of periodically detecting status of users corresponding to dynamic ND snooping binding entries is disabled.
3. Run nd user-bind detect retransmit retransmit-times interval retransmit-interval
  
  The number of times and interval for sending NS packets to detect the user status are configured.
  
  By default, the number of detection times is 2 and the detection interval is 1000 milliseconds.
Detection triggered by a conflicting NA packet:
1. Run system-view
  The system view is displayed.
2. Run nd snooping wait-time wait-time life-time life-time
  
  The wait time for a device to send an NS packet to detect the user status and the lifetime of an ND snooping binding entry within a detection interval are configured.
  
  By default, the wait time for a device to send an NS packet to detect the user status is 250 milliseconds and the lifetime of an ND snooping binding entry when a device detects the user status is 500 milliseconds.