Brocade Multi-Service IronWare Switching Configuration Guide (Supporting R05.6.00) - Manual (Page 795)

Multi-Service IronWare Switching Configuration Guide 765
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DHCP option 82 insertion
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• Vendor-Specific (suboption 9) —Contains the Internet Assigned Numbers Authority (IANA)
enterprise number (4874) and the layer 2 circuit ID and the user packet class.
Suboption 1 and suboption 2 are usually determined by the client network access device and
depend on the network configuration.
Suboption 9 can be used to associate specific data with the DHCP messages relayed between the
DHCP relay and the DHCP server. The suboption 9 can include the client’s IEEE 802.1p value,
which identifies the client's user priority.
Brocade(config)# ip dhcp-snooping vlan 10 insert-relay-information apend
Syntax: [no] ip dhcp-snooping vlan vlan-number insert-relay-information [append type]
The vlan-number variable specifies the ID of a configured client or DHCP server VLAN.
Use the append option to add suboption 9 in the option82 field of the DHCP request as per
RFC4342 before forwarding to server.
The type options to specify the sub option's type (suboption 1 and suboption 2). You can add a
suboption with a specific number. The range is between 3 and 254.
Enabling trust on a port
The default trust setting for a port is untrusted. To enable trust on a port connected to a DHCP
server, enter commands such as the following.
Brocade(config)#interface ethernet 1/1
Brocade(config-if-e10000-1/1)#dhcp-snooping-trust
Port 1/1 is connected to a DHCP server. The commands change the CLI to the interface
configuration level of port 1/1 and set the trust setting of port 1/1 to trusted.
Syntax: [no] dhcp-snooping-trust
Clearing the DHCP binding database
You can clear the DHCP binding database using the clear dhcp-binding command. You can remove
all entries in the database, or remove entries for a specific IP subnet, a VRF instance, or a VLAN id.
To remove all entries from the DHCP binding database, enter the following command.
Brocade#clear dhcp-binding
For example, to clear entries for a specific IP subnet, enter a command such as the following.
Brocade#clear dhcp 10.10.102.4
Syntax: clear dhcp [ip subnet] [vlan vlan_id] [vrf vrf_name]
The vlan_id variable specifies the ID of a configured VLAN.
The vrf_name variable specifies the VRF instance.
DHCP option 82 insertion
DHCP option 82 insertion can be used to assist DHCP servers to implement dynamic address
policy. When DHCP option 82 is present in DHCP packets, DHCP servers gets additional information
about the clients’ identity.