Defense Against ARP Spoofing Attacks

As shown in Figure 10-7, UserA, UserB, and UserC use Switch to connect to the gateway to access the Internet.

Generally, when UserA, UserB, and UserC go online and exchange ARP packets, ARP entries are created on UserA, UserB, UserC, and the gateway. At the same time, an attacker can send bogus ARP packets to UserA, UserB, UserC, or the gateway in the broadcast domain to modify ARP entries, obtain information, and obtain communication.

Figure 10-7 Defending against ARP spoofing attacks

To avoid the preceding problems, deploy ARP spoofing defense functions on the gateway, including rate ARP entry fixing, gratuitous ARP packet discarding, and strict ARP learning.

• After ARP entry fixing is deployed and the gateway learns an ARP entry for the first time, the gateway does not change the ARP entry, but only updates part of the entry, or sends a unicast ARP Request packet to check the validity of the ARP packet for updating the entry. This function prevents ARP entries from being modified by bogus ARP packets.

• After gratuitous ARP packet discarding is deployed, the gateway discards gratuitous ARP packets, preventing ARP entries from being modified by bogus ARP packets.

• After strict ARP learning is deployed, the gateway learns only the ARP Reply packets in response to the ARP Request packets that it has sent. This prevents ARP entries from being modified by bogus ARP packets.