Cisco Systems IE3010 Limiting the Rate of Incoming ARP Packets

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Cisco IE 3010 Switch Software Configuration Guide
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Chapter 22 Configuring Dynamic ARP Inspection
Configuring Dynamic ARP Inspection
To remove the ARP ACL, use the no arp access-list global configuration command. To remove the ARP
ACL attached to a VLAN, use the no ip arp inspection filter arp-acl-name vlan vlan-range global
configuration command.
This example shows how to configure an ARP ACL called host2 on Switch A, to permit ARP packets
from Host 2 (IP address 1.1.1.1 and MAC address 0001.0001.0001), to apply the ACL to VLAN 1, and
to configure port 1 on Switch A as untrusted:
Switch(config)# arp access-list host2
Switch(config-arp-acl)# permit ip host 1.1.1.1 mac host 1.1.1
Switch(config-arp-acl)# exit
Switch(config)# ip arp inspection filter host2 vlan 1
Switch(config)# interface gigabitethernet0/1
Switch(config-if)# no ip arp inspection trust
Limiting the Rate of Incoming ARP Packets
The switch CPU performs dynamic ARP inspection validation checks; therefore, the number of
incoming ARP packets is rate-limited to prevent a denial-of-service attack.
When the rate of incoming ARP packets exceeds the configured limit, the switch places the port in the
error-disabled state. The port remains in that state until you enable error-disabled recovery so that ports
automatically emerge from this state after a specified timeout period.
Note Unless you configure a rate limit on an interface, changing the trust state of the interface also changes
its rate limit to the default value for that trust state. After you configure the rate limit, the interface
retains the rate limit even when its trust state is changed. I f you enter the no ip arp inspection limit
interface configuration command, the interface reverts to its default rate limit.
For configuration guidelines for rate limiting trunk ports and EtherChann el ports, see the “Dynamic ARP
Inspection Configuration Guidelines” section on page 22-5.
Beginning in privileged EXEC mode, follow these steps to limit the rate of incoming ARP packets. This
procedure is optional.
Step 9 show arp access-list [acl-name]
show ip arp inspection vlan vlan-range
show ip arp inspection interfaces
Verify your entries.
Step 10 copy running-config startup-config (Optional) Save your entries in the configuration file.
Command Purpose
Command Purpose
Step 1 configure terminal Enter global configuration mode.
Step 2 interface interface-id Specify the interface to be rate-limited, and enter interface
configuration mode.