LevelOne GEL-5261, User Manual

Page: 316 / 570

Chapter 12
| Security Measures
DHCP Snooping
– 316 –
Configuring Ports
for DHCP Snooping
Use the Security > DHCP Snooping (Configure Interface) page to configure switch
ports as trusted or untrusted.
Command Usage
◆ A trusted interface is an interface that is configured to receive only messages
from within the network. An untrusted interface is an interface that is
configured to receive messages from outside the network or fire wall.
◆ When DHCP snooping is enabled both globally and on a VLAN, DHCP packet
filtering will be performed on any untrusted ports within the VLAN.
◆ When an untrusted port is changed to a trusted port, all the dynamic DHCP
snooping bindings associated with this port are removed.
◆
Set all ports connected to DHCP servers within the local network or fire wall to
trusted state. Set all other ports outside the local network or fire wall to
untrusted state.
◆ The format for TR101 option 82 is: “<IP> eth <SID>/<PORT>[:<VLAN>]”. Note
that the SID (Switch ID) is always 0. By default the PVID is added to the end of
the TR101 field for untagged packets. For tagged packets, the VLAN ID is always
added.
Parameters
These parameters are displayed:
◆ Trust Status – Enables or disables a port as trusted. (Default: Disabled)
◆ Max Number – The maximum number of DHCP clients which can be
supported per interface. (Range: 1-32; Default: 16)
◆
Circuit ID – Specifies DHCP Option 82 circuit ID suboption information.
■
Mode – Specifies the default string “VLAN -Unit- Port” or an arbitrary string.
(Default: VLAN-Unit-Port)
■
Value – An arbitrary string inserted into the circuit identifier field.
(Range: 1-32 characters)
■
TR101 VLAN Field – Adds “:VLAN” in TR101 field for untagged packets.
Web Interface
To configure global settings for DHCP Snooping:
1.
Click IP Service, DHCP, Snooping.
2.
Select Configure Interface from the Step list.
3.
Set any ports within the local network or firewall to trusted.