Users Guide

Internet 10.1.1.254 - 00:00:4d:69:e8:f2 Te 1/5/1 Vl 10 CP
Dell#
To see how many valid and invalid ARP packets have been processed, use the show arp inspection statistics
command.
Dell#show arp inspection statistics
Dynamic ARP Inspection (DAI) Statistics
---------------------------------------
Valid ARP Requests : 0
Valid ARP Replies : 1000
Invalid ARP Requests : 1000
Invalid ARP Replies : 0
Dell#
Bypassing the ARP Inspection
You can configure a port to skip ARP inspection by defining the interface as trusted, which is useful in multi-switch
environments.
ARPs received on trusted ports bypass validation against the binding table. All ports are untrusted by default.
To bypass the ARP inspection, use the following command.
• Specify an interface as trusted so that ARPs are not validated against the binding table.
INTERFACE mode
arp inspection-trust
Dynamic ARP inspection is supported on Layer 2 and Layer 3.
Source Address Validation
Using the DHCP binding table, Dell Networking OS can perform three types of source address validation (SAV).
Table 25. Three Types of Source Address Validation
Source Address Validation Description
IP Source Address Validation Prevents IP spoofing by forwarding only IP packets that have
been validated against the DHCP binding table.
DHCP MAC Source Address Validation Verifies a DHCP packet’s source hardware address matches
the client hardware address field (CHADDR) in the payload.
IP+MAC Source Address Validation Verifies that the IP source address and MAC source address
are a legitimate pair.
Enabling IP Source Address Validation
IP source address validation (SAV) prevents IP spoofing by forwarding only IP packets that have been validated against the
DHCP binding table.
A spoofed IP packet is one in which the IP source address is strategically chosen to disguise the attacker. For example, using
ARP spoofing, an attacker can assume a legitimate client’s identity and receive traffic addressed to it. Then the attacker can
spoof the client’s IP address to interact with other clients.
The DHCP binding table associates addresses the DHCP servers assign with the port or the port channel interface on which the
requesting client is attached and the VLAN the client belongs to. When you enable IP source address validation on a port, the
system verifies that the source IP address is one that is associated with the incoming port and optionally that the client belongs
to the permissible VLAN. If an attacker is impostering as a legitimate client, the source address appears on the wrong ingress
Dynamic Host Configuration Protocol (DHCP) 280