38-9
Cisco 7600 Series Router Cisco IOS Software Configuration Guide, Release 12.2SX
OL-4266-08
Chapter 38 Configuring Dynamic ARP Inspection
Configuring DAI
To apply an ARP ACL, perform this task:
When applying ARP ACLs, note the following information:
•
For
vlan_range
, you can specify a single VLAN or a range of VLANs:
–
To specify a single VLAN, enter a single VLAN number.
–
To specify a range of VLANs, enter a dash-separated pair of VLAN numbers.
–
You can enter a comma-separated list of VLAN numbers and dash-separated pairs of VLAN
numbers.
•
(Optional) Specify
static
to treat implicit denies in the ARP ACL as explicit denies and to drop
packets that do not match any previous clauses in the ACL. DHCP bindings are not used.
If you do not specify this keyword, it means that there is no explicit deny in the ACL that denies the
packet, and DHCP bindings determine whether a packet is permitted or denied if the packet does not
match any clauses in the ACL.
•
ARP packets containing only IP-to-MAC address bindings are compared against the ACL. Packets
are permitted only if the access list permits them.
This example shows how to apply an ARP ACL named example_arp_acl to VLANs 10 through 12 and
VLAN 15:
Router#
configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router(config)#
ip arp inspection filter example_arp_acl vlan 10-12,15
Router(config)#
do show ip arp inspection vlan 10-12,15 | begin Vlan
Vlan Configuration Operation ACL Match Static ACL
---- ------------- --------- --------- ----------
10 Enabled Inactive example_arp_acl No
11 Enabled Inactive example_arp_acl No
12 Enabled Inactive example_arp_acl No
15 Enabled Inactive example_arp_acl No
Vlan ACL Logging DHCP Logging
---- ----------- ------------
10 Deny Deny
11 Deny Deny
12 Deny Deny
15 Deny Deny
Configuring ARP Packet Rate Limiting
When DAI is enabled, the router performs ARP packet validation checks, which makes the router
vulnerable to an ARP-packet denial-of-service attack. ARP packet rate limiting can prevent an
ARP-packet denial-of-service attack.
Command
Purpose
Step 1
Router#
configure terminal
Enters global configuration mode.
Step 2
Router#
ip arp inspection filter
arp_acl_name
vlan
{
vlan_ID
|
vlan_range
} [
static
]
Applies the ARP ACL to a VLAN.
Step 3
Router(config)#
do show ip arp inspection vlan
{
vlan_ID
|
vlan_range
}
Verifies your entries.