Owner`s manual

Dynamic Host Configuration Protocol (DHCP) | 99
To see how many valid and invalid ARP packets have been processed, use the show arp inspection statistics
command (Figure 6-10).
Figure 6-10. Command example: show arp inspection database
Bypass 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.
Source Address Validation
Using the DHCP binding table, FTOS can perform three types of source address validation (SAV):
• IP Source Address Validation on page 100: prevents IP spoofing by forwarding only IP packets that
have been validated against the DHCP binding table.
• DHCP MAC Source Address Validation on page 100: verifies a DHCP packet’s source hardware
address matches the client hardware address field (CHADDR) in the payload.
• IP+MAC Source Address Validation on page 100: verifies that the IP source address and MAC source
address are a legitimate pair.
Task Command Syntax Command Mode
Specify an interface as trusted so that ARPs are not
validated against the binding table.
arp inspection-trust
INTERFACE
FTOS Behavior: Introduced in FTOS version 8.2.1.0, DAI was available for Layer 3 only. FTOS
version 8.2.1.1 extends DAI to Layer 2.
FTOS#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
FTOS#