Cisco Catalyst 3750-E - Page 626

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Catalyst 3750-E and 3560-E Switch Software Configuration Guide
OL-9775-08
Chapter 23 Configuring Dynamic ARP Inspection
Configuring Dynamic ARP Inspection
To disable dynamic ARP inspection, use the no ip arp inspection vlan vlan-range global configuration
command. To return the interfaces to an untrusted state, use the no ip arp inspection trust interface
configuration command.
This example shows how to configure dynamic ARP inspection on Switch A in VLAN 1. You would
pe
rform a similar procedure on Switch B:
Switch(config)# ip arp inspection vlan 1
Switch(config)# interface gigabitethernet
1/0/1
Switch(config-if)# ip arp inspection trust
Step 3
ip arp inspection vlan vlan-range Enable dynamic ARP inspection on a per-VLAN basis. By
default, dynamic ARP inspection is disabled on all VLANs.
For v
lan-range, specify a single VLAN identified by VLAN ID
number, a range of VLANs separated by a hyphen, or a series of
VLANs separated by a comma. The range is 1 to 4094.
Specify the same VLAN ID for both switches.
Step 4
interface interface-id Specify the interface connected to the other switch, and enter
interface configuration mode.
Step 5
ip arp inspection trust Configure the connection between the switches as trusted.
By default, all interfaces are untrusted.
The switch does not check ARP packets that it receives from the
o
ther switch on the trusted interface. It simply forwards the
packets.
For untrusted interfaces, the switch intercepts all ARP requests
a
nd responses. It verifies that the intercepted packets have valid
IP-to-MAC address bindings before updating the local cache and
before forwarding the packet to the appropriate destination. The
switch drops invalid packets and logs them in the log buffer
according to the logging configuration specified with the ip arp
inspection vlan logging global configuration command. For
more information, see the “Configuring the Log Buffer” section
on page 23-13.
Step 6
end Return to privileged EXEC mode.
Step 7
show ip arp inspection interfaces
show ip arp inspection vlan v
lan-range
Verify the dynamic ARP inspection configuration.
Step 8
show ip dhcp snooping binding Verify the DHCP bindings.
Step 9
show ip arp inspection statistics vlan
vlan-range
Check the dynamic ARP inspection statistics.
Step 10
copy running-config startup-config (Optional) Save your entries in the configuration file.
Command Purpose