Limiting The Rate Of Incoming Arp Packets - Cisco WS-CBS3032-DEL Software Configuration Manual

Configuring Dynamic ARP Inspection
Command
Step 7
no ip arp inspection trust
Step 8 end
Step 9 show arp access-list [acl-name]
show ip arp inspection vlan vlan-range
show ip arp inspection interfaces
Step 10
copy running-config startup-config
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 gigabitethernet1/0/1
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.
Unless you configure a rate limit on an interface, changing the trust state of the interface also changes
Note
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. If you enter the no ip arp inspection limit interface
configuration command, the interface reverts to its default rate limit.
Cisco Catalyst Blade Switch 3130 and 3032 for Dell Software Configuration Guide
23-10
Chapter 23 Configuring Dynamic ARP Inspection
Purpose
Configure the Switch A interface that is connected to
Switch B as untrusted.
By default, all interfaces are untrusted.
For untrusted interfaces, the switch intercepts all
ARP requests and 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.
Return to privileged EXEC mode.
Verify your entries.
(Optional) Save your entries in the configuration file.
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