And Dhcp Server (Cli Procedure) - Juniper JUNOS OS 10.3 - SOFTWARE Manual

Complete Software Guide for Junos
Setting Up DHCP Option 82 with the Switch as a Relay Agent Between Clients and
DHCP Server (CLI Procedure)
2926
®
OS for EX Series Ethernet Switches, Release 10.3
You can use DHCP option 82, also known as the DHCP relay agent information option,
to help protect the EX Series switch against attacks such as spoofing (forging) of IP
addresses and MAC addresses, and DHCP IP address starvation. Option 82 provides
information about the network location of a DHCP client, and the DHCP server uses this
information to implement IP addresses or other parameters for the client.
You can configure the DHCP option 82 feature in two topologies:
The switch functions as a relay agent when the DHCP clients or the DHCP server is
connected to the switch through a Layer 3 interface. On the switch, these interfaces
are configured as routed VLAN interfaces, or RVIs. The switch relays the clients' requests
to the server and then forwards the server's replies to the clients. This topic describes
this configuration.
The switch, DHCP clients, and DHCP server are all on the same VLAN. The switch
forwards the clients' requests to the server and forwards the server's replies to the
clients. This configuration is described in "Setting Up DHCP Option 82 on the Switch
with No Relay Agent Between Clients and DHCP Server (CLI Procedure)" on page 2929.
Before you configure DHCP option 82 on the switch, perform these tasks:
Connect and configure the DHCP server.
NOTE: Your DHCP server must be configured to accept DHCP option 82.
If the server is not configured for DHCP option 82, the server does not use
the DHCP option 82 information in the requests sent to it when it formulates
its reply messages.
Configure the VLAN on the switch and associate the interfaces on which the clients
connect to the switch with that VLAN.
Configure the routed VLAN interface (RVI) to allow the switch to relay packets to the
server and receive packets from the server. See "Configuring Routed VLAN Interfaces
(CLI Procedure)" on page 1379.
Configure the switch as a BOOTP relay agent. See "DHCP/BOOTP Relay for EX Series
Switches Overview" on page 548.
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