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DHCP Default Options
Option
DHCP Snooping
Option 82 Insertion
Option 82 Passthrough
Verify MAC Address
Backup DHCP Snooping Binding Database
Configuring DHCP Work Flow
To configure DHCP Snooping, do the following:
STEP 1 Enable DHCP Snooping in the Configuration > IP Network Operations
> DHCP Snooping page
STEP 2 Define the interfaces on which DHCP Snooping is enabled in the
Configuration > IP Network Operations> DHCP>DHCP Interfaces
page
STEP 3 Configure interfaces as trusted or untrusted in the Configuration > IP
Network Operations> DHCP > Trust Interfaces page
STEP 4 Optional Add entries to the DHCP Snooping Binding database in the
Configuration >IP Network Operations> DHCP Snooping Binding
Database page
DHCP Snooping
This section describes how the DHCP Snooping features are implemented via
the Web-based interface
In Layer 2, DHCP Snooping can only be enabled on VLANs with IP addresses
To globally configure DHCP Snooping, do the following:
STEP 1 Click Configuration > IP Network Operations > DHCP > DHCP
Snooping
STEP 2 To enable DHCP Snooping enter the following fields:
•
DHCP Snooping—Select to enable DHCP Snooping
Option 82 Passthrough—Select to leave foreign Option 82 information
•
when forwarding packets
Default State
Disable
Not enabled
Not enabled
Enabled
Not enabled
•
Verify MAC Address—Select to verify that the source MAC address of the
Layer 2 header matches the client hardware address as appears in the
DHCP Header (part of the payload) on DHCP untrusted ports
•
Backup Database—Select to back up the DHCP Snooping Binding
database on the device's flash memory
DHCP Interfaces
DHCP Snooping can be enabled on any interface with an IP Address, and on
VLANs with or without an IP address
To enable DHCP Snooping on specific interfaces, do the following:
STEP 1 Click Configuration > IP Network Operations > DHCP > DHCP
Interfaces
The following fields are displayed for each interface for which the features
are enabled:
•
Interface—On which DHCP Snooping is enabled or disabled
•
Interface IP Address—IP address of the interface on which DHCP
Snooping is enabled
•
DHCP Snooping—Select to enable DHCP snooping
STEP 2 To enable DHCP Snooping on an interface, click ADD
STEP 3 Select the interface and the feature to be enabled: DHCP Snooping
STEP 4 Click Apply The settings are written to the Running Configuration file
Trusted Interface
Packets from untrusted ports/LAGs are checked against the DHCP Snooping
Binding database (see the DHCP Snooping Binding Database page)
By default, interfaces are untrusted
To designate an interface as untrusted go to Interface Settings
DHCP Snooping Binding Database
Note the following points about maintenance of the DHCP Snooping
Binding database:
•
The device does not update the DHCP Snooping Binding database when
a station moves to another interface
•
If a port is down, the entries for that port are not deleted
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