In the realm of networking, DHCP (Dynamic Host Configuration Protocol) services play a pivotal role in assigning IP addresses automatically to devices within a network. However, this convenience is susceptible to security threats, one of which is ARP (Address Resolution Protocol) Spoofing.
ARP Spoofing involves an attacker sending falsified MAC addresses instead of genuine ones, redirecting network traffic toward their machine. By manipulating ARP messages, the attacker’s MAC address gets registered as the Default Gateway in the ARP Cache of target devices. Consequently, legitimate traffic meant for the Gateway gets diverted to the attacker’s machine, allowing them to intercept and potentially manipulate data.
To combat such threats, Cisco devices offer Dynamic ARP Inspection (DAI), a security feature akin to DHCP Snooping. DAI leverages Trusted and Untrusted ports within the network. Ports marked as Trusted can receive ARP replies, while Untrusted ports undergo a validation process where ARP information is cross-checked against the DHCP binding table. If a discrepancy arises, the port is deactivated, mitigating potential ARP Spoofing attacks.
This article elucidates the crucial role DHCP services play and how ARP Spoofing can compromise network security. Furthermore, it dives into the implementation of Dynamic ARP Inspection on Cisco devices as a preventive measure against such malicious activities.
A hacker can send a forged MAC address instead of the real MAC address, such as the Default Gateway, in response to an ARP message to network computers. In this scenario, the hacker’s computer address is placed as the Default Gateway in the user computer’s ARP Cache table, directing all traffic toward the hacker. The hacker then captures the traffic and forwards it to the actual Gateway. Using the capability of DAI, which is very similar to DHCP Snooping, and leveraging Trusted and Untrusted ports, greater resistance against ARP Spoofing attacks can be achieved.
Switch(config)#ip arp inspection vlan 1 will enable the DAI capability on VLAN 1.
Switch(config-if)#ip arp inspection trust