Chapter 26 IP Source Guard
GS2200-24 User’s Guide
239
26.12.2.2 Trusted 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.
26.12.2.3 Syslog
The Switch can send syslog messages to the specified syslog server (Chapter 35
on page 303) 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.
26.12.2.4 Configuring ARP Inspection
Follow these steps to configure ARP inspection on the Switch.
1 Configure DHCP snooping. See Section 26.12.1.4 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.
2 Enable ARP inspection on each VLAN.
3 Configure trusted and untrusted ports, and specify the maximum number of ARP
packets that each port can receive per second.
