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23 DHCP Snooping
Figure 23-14 Example configuration when a DHCP relay agent is connected under the
You can configure DHCP snooping as described in 23.2.3 Basic configuration (when DHCP
snooping is performed via a Layer 3 switch). In this example, because the DHCP relay
agent sends DHCP packets with Option 82, you need to set the Switch so that it permits
forwarding of the packets with Option 82 on untrusted ports to which the DHCP relay agent
is connected. In addition, you need to configure the following settings: not checking the
source address in DHCP packets on the same untrusted port, permitting the forwarding of
ARP packets, and using only IP addresses for terminal filtering.
To configure the above settings, use configuration commands.
(1) Setting of permitting reception of the packets with Option 82 on untrusted ports
Points to note
Sets that DHCP packets with Option 82 can be received on untrusted ports.
Command examples
1.
(config)# ip dhcp snooping information option allow-untrusted
Sets that DHCP packets with Option 82 can be received on untrusted ports.
(2) Setting of canceling the check for the source addresses in DHCP packets on
untrusted ports
Points to note
The following example sets the cancellation of the address check functionality so
that the source MAC address in a DHCP packet is forwarded on an untrusted port
without checking.
Command examples
1.
(config)# no ip dhcp snooping verify mac-address
Sets the configuration so that the source MAC addresses in DHCP packets received
on untrusted ports are not to be checked.
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