Web Management Guide-R03

Table Of Contents
Chapter 12
| Security Measures
DHCP Snooping
– 348
If DHCP Snooping Information Option 82 is enabled on the switch, information
may be inserted into a DHCP request packet received over any VLAN
(depending on DHCP snooping filtering rules). The information inserted into
the relayed packets includes the circuit-id and remote-id, as well as the
gateway Internet address.
When the switch receives DHCP packets from clients that already include DHCP
Option 82 information, the switch can be configured to set the action policy for
these packets. The switch can either drop the DHCP packets, keep the existing
information, or replace it with the switch’s relay information.
DHCP Snooping Information Option 82 cannot both be enabled at the same
time.
DHCP Snooping
Global Configuration
Use the IP Service > DHCP > Snooping (Configure Global) page to enable DHCP
Snooping globally on the switch, or to configure MAC Address Verification.
Parameters
These parameters are displayed:
DHCP Snooping Status – Enables DHCP snooping globally. (Default: Disabled)
DHCP Snooping MAC-Address Verification – Enables or disables MAC
address verification. If the source MAC address in the Ethernet header of the
packet is not same as the client's hardware address in the DHCP packet, the
packet is dropped. (Default: Enabled)
DHCP Snooping Information Option Status – Enables or disables DHCP
Option 82 information relay. (Default: Disabled)
DHCP Snooping Information Option Sub-option Format – Enables or
disables use of sub-type and sub-length fields in circuit-ID (CID) and remote-ID
(RID) in Option 82 information.
DHCP Snooping Information Option Remote ID – Specifies the MAC address,
IP address, or arbitrary identifier of the requesting device (i.e., the switch in this
context).
MAC Address Inserts a MAC address in the remote ID sub-option for the
DHCP snooping agent (i.e., the MAC address of the switch’s CPU). This
attribute can be encoded in Hexadecimal or ASCII.
IP Address – Inserts an IP address in the remote ID sub-option for the
DHCP snooping agent (i.e., the IP address of the management interface).
This attribute can be encoded in Hexadecimal or ASCII.
string - An arbitrary string inserted into the remote identifier field.
(Range: 1-32 characters)