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Configuration Guide - Security

S1720, S2700, S5700, and S6720 V200R011C10

This document describes the configurations of Security, including 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, MPAC, separating the management plane from the service plane, security risks, PKI.
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Optimized ARP Reply

Optimized ARP Reply

In Figure 7-2, when a stack functions as an access gateway, the stack can receive a large number of ARP packets requesting for the stack's interface MAC address. If all these ARP Request packets are sent to the master switch, the CPU usage of the switch 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 stack performs the following operations:
  • When receiving an ARP Request packet of which the destination IP address is the local interface address, the switch where the interface is located directly returns an ARP Reply packet.
  • When a stack system 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 master switch, the switch where the interface is located checks whether the ARP Request packet meets the proxy condition. If so, the switch returns an ARP Reply packet. If not, the switch discards the packet.
The optimized ARP reply function can be configured on a stand-alone fixed switch, but does not take effect.
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 stack performs optimized ARP reply to this ARP Request packet.
  • If the corresponding ARP entry does not exist, the stack does not perform optimized ARP reply to this ARP Request packet.
Updated: 2019-03-28

Document ID: EDOC1000178177

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