icmp-reply fast

Usage Scenario

The ping program is used to check network connectivity. If two hosts cannot ping each other, they cannot set up a connection. The ping program uses the ICMP protocol. It encapsulates ICMP Echo Request packets into IP packets, and sends the packets to the destination host. The destination host returns an ICMP Echo Reply packet to the source host. If the source host receives a reply within a certain period, the source host considers that the destination host is reachable.

In normal situations, after an interface receives an ICMP Echo Request packet, this packet is sent to the protocol stack and handled by the CPU.

After ICMP fast reply is enabled, if an interface receives an ICMP Echo Request packet of which the destination address is the local address, the packet is not sent to the protocol stack for handing by the CPU, but handled by the interface. This improves forwarding performance of the device.

Precautions

The fast ICMP reply function does not take effect on VBDIF interfaces.

In V200R010C00 and later versions, the fast ICMP reply function takes effect on sub-interfaces of the S5720-HI, S5730-HI, S5731-H, S5731-S, S5731S-S, S5731S-H, S5732-H, S6720-HI, S6730-H, S6730S-H, S6730-S, and S6730S-S.

For the S5720-HI, S5730-HI, S5731-H, S5731-S, S5731S-H, S5731S-S, S5732-H, S6720-HI, S6730-H, S6730S-H, S6730-S, and S6730S-S, after fast ICMP reply is enabled, the ping detection cannot be blocked by the blacklist. This is because after the fast ICMP reply function is enabled, the ICMP Echo Request packets received on an interface of the device are not sent to the protocol stack or processed by the CPU. Instead, the interface directly processes the packets.