Configuring the Optimized ND Reply Function

Context

When a stack functions as an access gateway, it receives a large number of ND Request packets that request the switch to reply with its local interface MAC address. If all these ND Request packets are sent to the master switch, the CPU usage of the master switch increases, and other services are affected.

The optimized ND reply function addresses this issue. After this function is enabled, the switch receiving an ND Request packet returns an ND Reply packet if the ND Request packet is destined for a local interface on the switch of the stack, and discards the ND Request packet if the packet is not destined for a local interface on the switch of the stack.

By default, the optimized ND reply function is enabled. After receiving an ND Request packet, the switch checks whether an ND entry corresponding to the source IPv6 address of the ND Request packet exists.

If the corresponding ND entry exists and the packet information is the same as the saved ND entry information, the switch performs optimized ND reply to this ND Request packet.
If the corresponding ND entry exists but the packet information differs from the saved ND entry information, the switch does not perform optimized ND reply to this ND Request packet.
If the corresponding ND entry does not exist, the switch does not perform optimized ND reply to this ND Request packet.

Procedure

Run system-view

The system view is displayed.
Run undo nd optimized-reply disable

The optimized ND reply function is enabled.

By default, the optimized ND reply function is enabled.
- The optimized ND reply function takes effect for ND Request packets sent by wireless users.
- The optimized ND reply function takes effect for ND Request packets received on VLANIF interfaces and VBDIF interfaces enabled with IPv6. VLANIF interfaces of Group VLANs and Separate VLANs in MUX VLANs, VLANIF interfaces of mapped VLANs, and VLANIF interfaces of super-VLANs do not perform optimized ND reply.
- If the number of global unicast IPv6 addresses on a VLANIF interface or VBDIF interface enabled with IPv6 exceeds 1, the switch does not perform optimized ND reply for NS packets received on this interface.
- If the ND snooping function is enabled on a switch, the switch does not perform optimized ND reply to received ND Request packets.
- The switch does not perform optimized ND reply to the following received packets:
  - NS packets with the source IPv6 address :: (that is, Duplicate Address Detection packets)
  - Packets with IPv6 extension headers

Verifying the Configuration

Run the display nd optimized-reply status command to check the status of the optimized ND reply function.
Run the display nd optimized-reply statistics [ slot slot-id ] command to check statistics on optimized ND Reply packets.