Concept Guide
Congure the System for User Port Stacking (Option
230)
Set the stacking-option variable to provide stack-port detail on the DHCP server when you set the DHCP oer. A stack can be formed
when the units are connected.
Option 230 is the option for user port stacking. Use it to create up to eight stack groups. Dene the conguration parameters on the DHCP
server for each chassis based on the chassis MAC address. Congure the following parameters:
• unit number
• priority
• stack group ID
The received stacking conguration is always applied on the master stack unit.
option #230 "unit-number:3#priority:2#stack-group:14"
Congure Secure DHCP
DHCP as dened by RFC 2131 provides no authentication or security mechanisms. Secure DHCP is a suite of features that protects
networks that use dynamic address allocation from spoong and attacks.
• Option 82
• DHCP Snooping
• Dynamic ARP Inspection
• Source Address Validation
Option 82
RFC 3046 (the relay agent information option, or Option 82) is used for class-based IP address assignment.
The code for the relay agent information option is 82, and is comprised of two sub-options, circuit ID and remote ID.
Circuit ID
This is the interface on which the client-originated message is received.
Remote ID This identies the host from which the message is received. The value of this sub-option is the MAC address of
the relay agent that adds Option 82.
In DHCPv4 relay , the Option 82 is not added by default. When the ip dhcp relay information-option is congured, the Option
82 with sub-options 1 (Agent Circuit ID) and 2 ( Agent Remote ID) are added to the relayed DHCP packet. The default values of the sub-
options are as follows:
• Default Agent Circuit ID is constructed in the format “VlanID:LagID:SlotId:PortId”
• Default Agent Remote ID is the system MAC address (in binary format)
The following example shows the format of the Circuit ID - 723:0:1:1
Table 26. Circuit ID Format
VLAN ID LAG ID Slot ID Port ID
723 0 1 1
The DHCP relay agent inserts Option 82 before forwarding DHCP packets to the server. The server can use this information to:
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Dynamic Host Conguration Protocol (DHCP)