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DHCP Snooping VLAN Configuration
Use the DHCP Snooping VLAN Configuration page to enable or disable DHCP
snooping on specific VLANs.
Command Usage
• When DHCP snooping is enabled globally on the switch, and enabled on the
specified VLAN, DHCP packet filtering will be performed on any untrusted ports
within the VLAN.
• When the DHCP snooping is globally disabled, DHCP snooping can still be
configured for specific VLANs, but the changes will not take effect until DHCP
snooping is globally re-enabled.
• When DHCP snooping is globally enabled, and DHCP snooping is then disabled
on a VLAN, all dynamic bindings learned for this VLAN are removed from the
binding table.
Command Attributes
• VLAN ID – ID of a configured VLAN. (Range: 1-4094)
• DHCP Snooping Status – Enables or disables DHCP snooping for the selected
VLAN. When DHCP snooping is enabled globally on the switch, and enabled on
the specified VLAN, DHCP packet filtering will be performed on any untrusted ports
within the VLAN.
Web – Click DHCP Snooping, VLAN Configuration.
CLI – This example first enables DHCP Snooping for VLAN 1.
Console(config)#ip dhcp snooping vlan 1
Console(config)#
DHCP Snooping Information Option Configuration
DHCP provides a relay mechanism for sending information about the switch and its
DHCP clients to the DHCP server. Known as DHCP Option 82, it allows compatible
DHCP servers to use the information when assigning IP addresses, or to set other
services or policies for clients. It is also an effective tool in preventing malicious
network attacks from attached clients on DHCP services, such as IP Spoofing, Client
Identifier Spoofing, MAC Address Spoofing, and Address Exhaustion.
Figure 3-63 DHCP Snooping VLAN Configuration
Access Control Lists
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3-103
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