Juniper JUNOS OS 10.4 - FOR EX REV 1 Manual page 3169

Suboption Components of Option 82
Copyright © 2010, Juniper Networks, Inc.
address or another parameter for the client. See "Suboption Components of Option 82"
on page 3065 for details about option 82 information.
You can enable DHCP option 82 on a single VLAN or on all VLANs on the switch. You can
also configure it on Layer 3 interfaces (in routed VLAN interfaces, or RVIs) when the
switch is functioning as a relay agent.
When option 82 is enabled on the switch, then this sequence of events occurs when a
DHCP client sends a DHCP request:
The switch receives the request and inserts the option 82 information in the packet
1.
header.
The switch forwards or relays the request to the DHCP server.
2.
The server uses the DHCP option 82 information to formulate its reply and sends a
3.
response back to the switch. It does not alter the option 82 information.
The switch strips the option 82 information from the response packet.
4.
The switch forwards the response packet to the client.
5.
NOTE: To use the DHCP option 82 feature, you must ensure that the DHCP
server is configured to accept option 82. If it is not configured to accept
option 82, then when it receives requests containing option 82 information,
it does not use the information in setting parameters and it does not echo
the information in its response message. For detailed information about
configuring DHCP services, see the
The configuration for DHCP service on the Juniper Networks EX Series Ethernet
Switch includes the
level.
Option 82 as implemented on the EX Series switch comprises the suboptions circuit ID,
remote ID, and vendor ID. These suboptions are fields in the packet header:
circuit ID—Identifies the circuit (interface and/or VLAN) on the switch on which the
request was received. The circuit ID contains the interface name and/or VLAN name,
with the two elements separated by a colon—for example,
ge-0/0/10 is the interface name and
received on a Layer 3 interface, the circuit ID is just the interface name—for example,
.
ge-0/0/10
Use the prefix option to add an optional prefix to the circuit ID. If you enable the
option, the hostname for the switch is used as the prefix; for example,
switch1:ge-0/0/10:vlan1
You can also specify that the interface description be used rather than the interface
name and/or that the VLAN ID be used rather than the VLAN name.
Junos OS System Basics Configuration Guide.
dhcp statement at the
vlan1 is the VLAN name. If the request packet is
, where is the hostname.
switch1
Chapter 99: Port Security Overview
[edit system services] hierarchy
, where
ge-0/0/10:vlan1
prefix
3065