Juniper JUNOS OS 10.3 - SOFTWARE, Manual

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•
Configured the switch as a BOOTP relay agent. See “DHCP/BOOTP Relay for EX Series
Switches Overview” on page 548.
• Configured 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.
Overview and Topology
If DHCP option 82 is enabled on the switch, then when a network device—a DHCP
client—that is connected to the switch on an untrusted interface sends a DHCP request,
the switch inserts information about the client's network location into the packet header
of that request. The switch then sends the request (in this setting, it relays the request)
to the DHCP server. The DHCP server reads the option 82 information in the packet header
and uses it to implement the IP address or other parameter for the client.
When option 82 is enabled on the switch, then this sequence of events occurs when a
DHCP client sends a DHCP request:
1.
The switch receives the request and inserts the option 82 information in the packet
header.
2.
The switch relays the request to the DHCP server.
3.
The server uses the DHCP option 82 information to formulate its reply and sends a
response back to the switch. It does not alter the option 82 information.
4.
The switch strips the option 82 information from the response packet.
5.
The switch forwards the response packet to the client.
In this example, you configure option 82 on the EX Series switch. The switch is configured
as a BOOTP relay agent. The switch connects to the DHCP server through the routed
VLAN interface (RVI) that you configured. The switch and clients are members of the
employee
VLAN. The DHCP server is a member of the
corporate
VLAN.
Configuration
To configure DHCP option 82:
CLI Quick
Configuration
To quickly configure DHCP option 82, copy the following commands and paste them
into the switch terminal window:
set forwarding-options helpers bootp dhcp-option82
set forwarding-options helpers bootp dhcp-option82 circuit-id prefix hostname
set forwarding-options helpers bootp dhcp-option82 circuit-id use-vlan-id
set forwarding-options helpers bootp dhcp-option82 remote-id
set forwarding-options helpers bootp dhcp-option82 remote-id prefix mac
set forwarding-options helpers bootp dhcp-option82 remote-id use-string employee-switch1
set forwarding-options helpers bootp dhcp-option82 vendor-id
Copyright © 2010, Juniper Networks, Inc. 2896
Complete Software Guide for Junos
®
OS for EX Series Ethernet Switches, Release 10.3