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Configuration Guide - Security

S7700 and S9700 V200R011C10

This document describes the configurations of Security, including ACL, reflective ACL, local attack defense, MFF, attack defense, traffic suppression and storm control, ARP security, port security, DHCP snooping, ND snooping, PPPoE+, IPSG, SAVI, URPF, keychain, separating the management plane from the service plane, security risks.
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Optimized ARP Reply

Optimized ARP Reply

In Figure 7-2, the gateway receives a large number of ARP Request packets to request its interface MAC address. If all these ARP Request packets are sent to the CPU, the CPU usage of the MPU increases, and other services are affected.

Figure 7-2  Networking of optimized ARP reply
To address the preceding problem, enable optimized ARP reply, which improves the switch's capability of defending against ARP flood attack. After this function is enabled, the switch performs the following operations:
  • When receiving an ARP Request packet of which the destination IP address is the local interface address, the LPU directly returns an ARP Reply packet.
  • When a switch receives an ARP Request packet of which the destination IP address is not the local interface address and intra-VLAN proxy ARP is enabled on the switch, the LPU checks whether the ARP Request packet meets the proxy condition. If so, the LPU returns an ARP Reply packet. If not, the LPU discards the packet.
The optimized ARP reply function is applicable to the device with multiple LPUs configured.
By default, the optimized ARP reply function is enabled. After a device receives an ARP Request packet, the device checks whether an ARP entry corresponding to the source IP address of the ARP Request packet exists.
  • If the corresponding ARP entry exists, the switch performs optimized ARP reply to this ARP Request packet.
  • If the corresponding ARP entry does not exist, the switch does not perform optimized ARP reply to this ARP Request packet.
Updated: 2019-04-01

Document ID: EDOC1000178319

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