R0106-HP MSR Router Series Layer 3 - IP Services Configuration Guide(V7)

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Table 5 Handling strategies
If a DHCP request
has…
Handling
strate
gy
DHCP snooping…
Option 82
Drop Drops the message.
Keep Forwards the message without changing Option 82.
Replace
Forwards the message after replacing the original Option 82 with
the Option 82 padded according to the configured padding format,
padding content, and code type.
No Option 82 N/A
Forwards the message after adding the Option 82 padded
according to the configured padding format, padding content, and
code type.
Feature and hardware compatibility
This feature is supported only on the following models:
MSR routers that hold an Layer 2 switching module.
DHCP snooping configuration task list
If you configure DHCP snooping settings on a Layer 2 Ethernet interface that has been added to an
aggregation group, the settings do not take effect unless the interface is removed from the aggregation
group.
Tasks at a glance
(Required.) Configuring basic DHCP snooping
(Optional.) Configuring Option 82
(Optional.) Saving DHCP snooping entries
(Optional.) Enabling DHCP starvation attack protection
(Optional.) Enabling DHCP-REQUEST attack protection
(Optional.) Setting the maximum number of DHCP snooping entries
Configuring basic DHCP snooping
Follow these guidelines when you configure basic DHCP snooping:
• Specify the ports connected to authorized DHCP servers as trusted ports to make sure that DHCP
clients can obtain valid IP addresses. The trusted ports and the ports connected to DHCP clients must
be in the same VLAN.
• Layer 2 Ethernet interfaces can be specified as trusted ports.
• DHCP snooping can work with QinQ to record VLAN tags for DHCP packets received from clients.
For more information about QinQ, see Layer 2—LAN Switching Configuration Guide.
To configure basic DHCP snooping: