Netgear M4300-24X24F (XSM4348S) - Stackable Managed Switch with 48x10G including 24x10GBASE-T and 24xSFP+ Layer 3 Guia Do Administrador

Dynamic ARP inspection (DAI) is a security feature that rejects invalid and malicious ARP 
packets. The feature prevents a class of man-in-the-middle attacks, where an unfriendly 
station intercepts traffic for other stations by poisoning the ARP caches of its unsuspecting 
neighbors. The miscreant sends ARP requests or responses mapping another station’s IP 
address to its own MAC address.

DAI relies on DHCP snooping. DHCP snooping listens to DHCP message exchanges and 
builds a bindings database of valid tuples (MAC address, IP address, VLAN interface).

When DAI is enabled, the switch drops ARP packet if the sender MAC address and sender IP 
address do not match an entry in the DHCP snooping bindings database. However, it can be 
overcome through static mappings. Static mappings are useful when hosts configure static IP 
addresses, DHCP snooping cannot be run, or other switches in the network do not run 
dynamic ARP inspection. A static mapping associates an IP address to a MAC address on a 
VLAN.

Static client
IP address: 192.168.10.1
HW address: 00:11:85:EE:54:E9

Interface
1/0/2

Switch

Interface
1/0/1

Interface
1/0/3

DHCP server
IP address: 192.168.10.1

DHCP client
IP address: 192.168.10.86 (obtained)
HW address: 00:16:76:A7:88:CC