C
HAPTER
24
| General Security Measures
ARP Inspection
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EXAMPLE
Console#show ip source-guard binding
MacAddress IpAddress Lease(sec) Type VLAN Interface
----------------- --------------- ---------- -------------------- ---- --------
11-22-33-44-55-66 192.168.0.99 0 Static 1 Eth 1/5
Console#
ARP INSPECTION
ARP Inspection validates the MAC-to-IP address bindings in Address
Resolution Protocol (ARP) packets. It protects against ARP traffic with
invalid address bindings, which forms the basis for certain “man-in-the-
middle” attacks. This is accomplished by intercepting all ARP requests and
responses and verifying each of these packets before the local ARP cache is
updated or the packet is forwarded to the appropriate destination,
dropping any invalid ARP packets.
ARP Inspection determines the validity of an ARP packet based on valid IP-
to-MAC address bindings stored in a trusted database – the DHCP snooping
binding database. ARP Inspection can also validate ARP packets against
user-configured ARP access control lists (ACLs) for hosts with statically
configured IP addresses.
This section describes commands used to configure ARP Inspection.
Table 84: ARP Inspection Commands
Command Function Mode
ip arp inspection Enables ARP Inspection globally on the switch GC
ip arp inspection filter Specifies an ARP ACL to apply to one or more VLANs GC
ip arp inspection log-buffer
logs
Sets the maximum number of entries saved in a log
message, and the rate at these messages are sent
GC
ip arp inspection validate Specifies additional validation of address
components in an ARP packet
GC
ip arp inspection vlan Enables ARP Inspection for a specified VLAN or range
of VLANs
GC
ip arp inspection limit Sets a rate limit for the ARP packets received on a
port
IC
ip arp inspection trust Sets a port as trusted, and thus exempted from ARP
Inspection
IC
show ip arp inspection
configuration
Displays the global configuration settings for ARP
Inspection
PE
show ip arp inspection
interface
Shows the trust status and inspection rate limit for
ports
PE
show ip arp inspection log Shows information about entries stored in the log,
including the associated VLAN, port, and address
components
PE
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