11-25
Configuring Advanced Threat Protection
Dynamic IP Lockdown
â– The DHCP binding database allows VLANs enabled for DHCP
snooping to be known on ports configured for dynamic IP lockdown.
As new IP-to-MAC address and VLAN bindings are learned, a corre-
sponding permit rule is dynamically created and applied to the port
(preceding the final deny any vlan <VLAN_IDs> rule as shown in the
example in Figure 11-4. These VLAN_IDs correspond to the subset of
configured and enabled VLANS for which DHCP snooping has been
configured.
â– For dynamic IP lockdown to work, a port must be a member of at
least one VLAN that has DHCP snooping enabled.
â– Disabling DHCP snooping on a VLAN causes Dynamic IP bindings on
Dynamic IP Lockdown-enabled ports in this VLAN to be removed. The
port reverts back to switching traffic as usual.
Filtering IP and MAC Addresses Per-Port and Per-VLAN
This section contains an example that shows the following aspects of the
Dynamic IP Lockdown feature:
â– Internal Dynamic IP lockdown bindings dynamically applied on a per-port
basis from information in the DHCP Snooping lease database and stati-
cally configured IP-to-MAC address bindings
â– Packet filtering using source IP address, source MAC address, and source
VLAN as criteria
In this example, the following DHCP leases have been learned by DHCP
snooping on port 5. VLANs 2 and 5 are enabled for DHCP snooping.
The following example shows an IP-to-MAC address and VLAN binding that
have been statically configured in the lease database on port 5.
Table 1. Sample DHCP Snooping Entries
IP Address MAC Address VLAN ID
10.0.8.5 001122-334455 2
10.0.8.7 001122-334477 2
10.0.10.3 001122-334433 5
IP Address MAC Address VLAN ID
10.0.10.1 001122-110011 5
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