Chapter 26 IP Source Guard

•They appear only in the ARP Inspection screens and commands, not in the MAC Address Filter screens and commands.

26.1.2.2Trusted vs. Untrusted Ports

Every port is either a trusted port or an untrusted port for ARP inspection. This setting is independent of the trusted/untrusted setting for DHCP snooping. You can also specify the maximum rate at which the Switch receives ARP packets on untrusted ports.

The Switch does not discard ARP packets on trusted ports for any reason.

The Switch discards ARP packets on untrusted ports in the following situations:

•The sender’s information in the ARP packet does not match any of the current bindings.

•The rate at which ARP packets arrive is too high.

26.1.2.3Syslog

The Switch can send syslog messages to the specified syslog server (Chapter 36 on page 331) when it forwards or discards ARP packets. The Switch can consolidate log messages and send log messages in batches to make this mechanism more efficient.

26.1.2.4 Configuring ARP Inspection

Follow these steps to configure ARP inspection on the Switch.

1Configure DHCP snooping. See Section 26.1.1.4 on page 237.

Note: It is recommended you enable DHCP snooping at least one day before you enable ARP inspection so that the Switch has enough time to build the binding table.

2Enable ARP inspection on each VLAN.

3Configure trusted and untrusted ports, and specify the maximum number of ARP packets that each port can receive per second.

26.2IP Source Guard

Use this screen to look at the current bindings for DHCP snooping and ARP inspection. Bindings are used by DHCP snooping and ARP inspection to distinguish between authorized and unauthorized packets in the network. The Switch learns

 

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MGS-3712/MGS-3712F User’s Guide