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Cisco IE 3010 Switch Software Configuration Guide
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Chapter 21 Configuring DHCP Features and IP Source Guard Features
Configuring IP Source Guard
traffic on nonrouted Layer 2 interfaces. It filters traffic based on the DHCP snooping binding database
and on manually configured IP source bindings. The previous version of IPSG required a DHCP
environment for IPSG to work.
IPSG for static hosts allows IPSG to work without DHCP. IPSG for static hosts relies on IP device
tracking-table entries to install port ACLs. The switch creates static entries based on ARP requests or
other IP packets to maintain the list of valid hosts for a given port. You can also specify the number of
hosts allowed to send traffic to a given port. This is equivalent to port security at L ayer 3.
IPSG for static hosts also supports dynamic hosts. If a dynamic hos t receives a DHCP-assigned IP
address that is available in the IP DHCP snooping table, the same entry is learned by the IP device
tracking table.When you enter the show ip device tracking all EXEC command, the IP device tracking
table displays the entries as ACTIVE.
Note Some IP hosts with multiple network interfaces can inject some invalid packets into a network
interface. The invalid packets contain the IP or MAC address for another network interface of
the host as the source address. The invalid packets can cause IPSG for static hosts to connect to
the host, to learn the invalid IP or MAC address bindings, and to reject the valid bindings.
Consult the vender of the corresponding operating system and the network interface to prevent
the host from injecting invalid packets.
IPSG for static hosts initially learns IP or MAC bindings dynamically through an ACL-based snooping
mechanism. IP or MAC bindings are learned from static hosts by ARP and IP pa ckets. They are stored
in the device tracking database. When the number of IP addre sses that have been dynamically learned or
statically configured on a given port reaches a maximum, the hardware drops any packet with a new IP
address. To resolve hosts that have moved or gone away for any reason, IPSG for static hosts leverages
IP device tracking to age out dynamically learned IP address bindings. This feature can be used with
DHCP snooping. Multiple bindings are established on a port that is connected to both DHCP and static
hosts. For example, bindings are stored in both the device tracking database as well as in the DHCP
snooping binding database.
Configuring IP Source Guard
• Default IP Source Guard Configuration, page 21-17
• IP Source Guard Configuration Guidelines, page 21-17
• Enabling IP Source Guard, page 21-18
• Configuring IP Source Guard for Static Hosts, page 21-19

Default IP Source Guard Configuration

By default, IP source guard is disabled.

IP Source Guard Configuration Guidelines

• 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: