Configure Secure Dhcp; Option 82 - Dell C9000 Series Networking Configuration Manual

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A switch can operate as a DHCP client and a DHCP server. DHCP client interfaces cannot acquire a dynamic

IP address from the DHCP server running on the switch. Acquire a dynamic IP address from another DHCP

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 Secure DHCP

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.

DHCP Snooping

Dynamic ARP Inspection

Source Address Validation

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

This is the interface on which the client-originated message is received.

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:

track the number of address requests per relay agent. Restricting the number of addresses available per

relay agent can harden a server against address exhaustion attacks.

associate client MAC addresses with a relay agent to prevent offering an IP address to a client spoofing

the same MAC address on a different relay agent.

assign IP addresses according to the relay agent. This prevents generating DHCP offers in response to

requests from an unauthorized relay agent.

Dynamic Host Configuration Protocol (DHCP)