4. The switching device strips the option 82 information from the response packet.
5. The switching device forwards the response packet to the client.
To use the DHCP option 82 feature, you must ensure that the DHCP server is configured
to accept option 82. If the DHCP server is not configured to accept option 82, then when
it receives requests containing option 82 information, it does not use the information for
setting parameters and it does not echo the information in its response message.
NOTE: If your switching device is an EX Series switch and uses Junos OS with
Enhanced Layer 2 Software (ELS) configuration style, you can enable DHCP
option 82 only for a specific VLAN. See Setting Up DHCP Option 82 on the
Switch with No Relay Agent Between Clients and DHCP Server (CLI Procedure).
If your switching device is an EX Series switch and does not use Junos OS
with Enhanced Layer 2 Software (ELS) configuration style, you can enable
DHCP option 82 either for a specific VLAN or for all VLANs. See Setting Up
DHCP Option 82 on the Switch with No Relay Agent Between Clients and DHCP
Server (CLI Procedure).
Suboption Components of Option 82
Option 82 as implemented on a switching device comprises the suboptions circuit ID,
remote ID, and vendor ID. These suboptions are fields in the packet header:
•
circuit ID—Identifies the circuit (interface or VLAN) on the switching device on which
the request was received. The circuit ID contains the interface name and VLAN name,
with the two elements separated by a colon—for example, ge-0/0/10:vlan1, where
ge-0/0/10 is the interface name and vlan1 is the VLAN name. If the request packet is
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 prefix
option, the hostname for the switching device is used as the prefix; for example,
device1:ge-0/0/10:vlan1, where device1 is the hostname.
You can also specify that the interface description be used rather than the interface
name or that the VLAN ID be used rather than the VLAN name.
•
remote ID—Identifies the remote host. See remote-id for details.
•
vendor ID—Identifies the vendor of the host. If you specify the vendor-id option but do
not enter a value, the default value Juniper is used. To specify a value, you type a
character string.
393Copyright © 2017, Juniper Networks, Inc.
Chapter 11: Configuring DHCP and DHCPv6 Relay Agent
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