Administrator Guide

Virtual Router Redundancy Protocol (VRRP)
Do not enable the DHCP client on an interface and set the priority to 255 or assign the same DHCP
interface IP address to a VRRP virtual group. Doing so guarantees that this router becomes the VRRP
group owner.
To use the router as the VRRP owner, if you enable a DHCP client on an interface that is added to a VRRP
group, assign a priority less than 255 but higher than any other priority assigned in the group.
Configure 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
offer. 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. Define the
configuration parameters on the DHCP server for each chassis based on the chassis MAC address.
Configure the following parameters:
• unit number
• priority
• stack group ID
The received stacking configuration is always applied on the master stack unit.
option #230 "unit-number:3#priority:2#stack-group:14"
Configure Secure DHCP
The following feature is available on the Z-Series platform, except where noted.
DHCP as defined 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 spoofing 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 identifies 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.
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 Configuration Protocol (DHCP)