38
Enhancements
Release L.10.09 Enhancements
Figure 14. Example of Authorized Servers for DHCP Snooping
Using DHCP Snooping with Option 82
DHCP adds Option 82 (relay information option) to DHCP request packets received on untrusted
ports by default. (See the preceding section
Configuring DHCP Relay
for more information on
Option 82.)
When DHCP is enabled globally and also enabled on a VLAN, and the switch is acting as a DHCP
relay, the settings for the DHCP relay Option 82 command are ignored when snooping is controlling
Option 82 insertion. Option 82 inserted in this manner allows the association of the client’s lease with
the correct port, even when another device is acting as a DHCP relay or when the server is on the
same subnet as the client.
N o t e
DHCP snooping only overrides the Option 82 settings on a VLAN that has snooping enabled, not
on VLANS without snooping enabled.
P
roCurve(config)# show dhcp-snooping
DHCP Snooping Information
DHCP Snooping : Yes
Enabled Vlans : 4
Verify MAC : No
Option 82 untrusted policy : drop
Option 82 Insertion : Yes
Option 82 remote-id : subnet-ip
Authorized Servers
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111.222.3.4
10.0.0.11
