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Catalyst 3560 Switch Software Configuration Guide
OL-8553-06
Chapter 21 Configuring DHCP Features and IP Source Guard
Configuring IP Source Guard
IP Source Guard Configuration Guidelines
These are the configuration guidelines for IP source guard:
• You can configure static IP bindings only on nonrouted ports. If you enter the ip source binding
mac-address vlan vlan-id ip-address interface interface-id global configuration command on a
routed interface, this error message appears:
Static IP source binding can only be configured on switch port.
• When IP source guard with source IP filtering is enabled on an interface, DHCP snooping must be
enabled on the access VLAN to which the interface belongs.
• If you are enabling IP source guard on a trunk interface with multiple VLANs and DHCP snooping
is enabled on all the VLANs, the source IP address filter is applied on all the VLANs.
Note If IP source guard is enabled and you enable or disable DHCP snooping on a VLAN on the
trunk interface, the switch might not properly filter traffic.
• When IP source guard with source IP and MAC address filtering is enabled, DHCP snooping and
port security must be enabled on the interface. You must also enter the ip dhcp snooping
information option global configuration command and ensure that the DHCP server supports
option 82. When IP source guard is enabled with MAC address filtering, the DHCP host MAC
address is not learned until the host is granted a lease. When forwarding packets from the server to
the host, DHCP snooping uses the option-82 data to identify the host port.
• When configuring IP source guard on interfaces on which a private VLAN is configured, port
security is not supported.
• IP source guard is not supported on EtherChannels.
• You can enable this feature when IEEE 802.1x port-based authentication is enabled.
• If the number of ternary content addressable memory (TCAM) entries exceeds the maximum
available, the CPU usage increases.
Enabling IP Source Guard
Beginning in privileged EXEC mode, follow these steps to enable and configure IP source guard on an
interface.
Command Purpose
Step 1
configure terminal Enter global configuration mode.
Step 2
interface interface-id Specify the interface to be configured, and enter interface configuration
mode.