Chapter 24 IP Source Guard
24.1.2.1 ARP Inspection and MAC Address Filters
When the Switch identifies an unauthorized ARP packet, it automatically creates a MAC address filter to block traffic from the source MAC address and source VLAN ID of the unauthorized ARP packet. You can configure how long the MAC address filter remains in the Switch.
These MAC address filters are different than regular MAC address filters (Chapter 10 on page 107).
•They are stored only in volatile memory.
•They do not use the same space in memory that regular MAC address filters use.
•They appear only in the ARP Inspection screens and commands, not in the MAC Address Filter screens and commands.
24.1.2.2Trusted 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.
24.1.2.3Syslog
The Switch can send syslog messages to the specified syslog server (Chapter 38 on page 309) 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.
24.1.2.4 Configuring ARP Inspection
Follow these steps to configure ARP inspection on the Switch.
1Configure DHCP snooping. See Section 24.1.1.4 on page 205.
"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.
206 |
| |
| ||
|
|
|