Chapter 23 Configuring Dynamic ARP Inspection

Configuring Dynamic ARP Inspection

Logging of Dropped Packets

When the switch drops a packet, it places an entry in the log buffer and then generates system messages on a rate-controlled basis. After the message is generated, the switch clears the entry from the log buffer. Each log entry contains flow information, such as the receiving VLAN, the port number, the source and destination IP addresses, and the source and destination MAC addresses.

You use the ip arp inspection log-bufferglobal configuration command to configure the number of entries in the buffer and the number of entries needed in the specified interval to generate system messages. You specify the type of packets that are logged by using the ip arp inspection vlan logging global configuration command. For configuration information, see the “Configuring the Log Buffer” section on page 23-12.

Configuring Dynamic ARP Inspection

These sections contain this configuration information:

Default Dynamic ARP Inspection Configuration, page 23-5

Dynamic ARP Inspection Configuration Guidelines, page 23-6

Configuring Dynamic ARP Inspection in DHCP Environments, page 23-7(required in DHCP environments)

Configuring ARP ACLs for Non-DHCP Environments, page 23-8(required in non-DHCP environments)

Limiting the Rate of Incoming ARP Packets, page 23-10(optional)

Performing Validation Checks, page 23-11(optional)

Configuring the Log Buffer, page 23-12(optional)

Default Dynamic ARP Inspection Configuration

Table 23-1shows the default dynamic ARP inspection configuration.

Table 23-1 Default Dynamic ARP Inspection Configuration

Feature

Default Setting

 

 

Dynamic ARP inspection

Disabled on all VLANs.

 

 

Interface trust state

All interfaces are untrusted.

 

 

Rate limit of incoming ARP packets

The rate is 15 pps on untrusted interfaces, assuming that

 

the network is a switched network with a host

 

connecting to as many as 15 new hosts per second.

 

The rate is unlimited on all trusted interfaces.

 

The burst interval is 1 second.

 

 

ARP ACLs for non-DHCP environments

No ARP ACLs are defined.

 

 

Validation checks

No checks are performed.

 

 

Catalyst 3750-E and 3560-E Switch Software Configuration Guide

 

OL-9775-02

23-5

 

 

 

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Cisco Systems 3750E manual Configuring Dynamic ARP Inspection, Logging of Dropped Packets, 23-5