Cisco 4500M User Manual

34-6
Software Configuration Guide—Release 12.2(25)EW
OL-6696-01
Chapter 34 Understanding and Configuring Dynamic ARP Inspection
Configuring Dynamic ARP Inspection
Step 3 Configure interface fa6/3 as trusted:
S1# conf t
Enter configuration commands, one per line. End with CNTL/Z.
S1(config)# in fa6/3
S1(config-if)# ip arp inspection trust
S1(config-if)# end
S1# show ip arp inspection interfaces fastEthernet 6/3
Interface Trust State Rate (pps)
--------------- ----------- ----------
Fa6/3 Trusted None
S1#
Step 4 Verify the bindings:
S1# show ip dhcp snooping binding
MacAddress IpAddress Lease(sec) Type VLAN Interface
------------------ --------------- ---------- ------------- ---- --------------------
00:02:00:02:00:02 1.1.1.2 4993 dhcp-snooping 1 FastEthernet6/4
S1#
Step 5 Check the statistics before and after Dynamic ARP processes any packets:
S1# show ip arp inspection statistics vlan 1
Vlan Forwarded Dropped DHCP Drops ACL Drops
---- --------- ------- ---------- ----------
1 0 0 0 0
Vlan DHCP Permits ACL Permits Source MAC Failures
---- ------------ ----------- -------------------
1 0 0 0
Vlan Dest MAC Failures IP Validation Failures
---- ----------------- ----------------------
1 0 0
S1#
If H1 then sends out two ARP requests with an IP address of 1.1.1.2 and a MAC address of
0002.0002.0002, both requests are permitted, as reflected in the following statistics:
S1# show ip arp inspection statistics vlan 1
Vlan Forwarded Dropped DHCP Drops ACL Drops
---- --------- ------- ---------- ----------
1 2 0 0 0
Vlan DHCP Permits ACL Permits Source MAC Failures
---- ------------ ----------- -------------------
1 2 0 0
Vlan Dest MAC Failures IP Validation Failures
---- ----------------- ----------------------
1 0 0
S1#
If H1 then tries to send an ARP request with an IP address of 1.1.1.3, the packet is dropped and an error
message is logged:
00:12:08: %SW_DAI-4-DHCP_SNOOPING_DENY: 2 Invalid ARPs (Req) on Fa6/4, vlan
1.([0002.0002.0002/1.1.1.3/0000.0000.0000/0.0.0.0/02:42:35 UTC Tue Jul 10 2001])
S1# show ip arp inspection statistics vlan 1
S1#

Cisco 4500M Specifications

General

Brand	Cisco
Model	4500M
Category	Network Router
Language	English