Juniper JUNOSE 11.0.X MULTICAST ROUTING, Configuration Manual

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Ethernet interfaces. Use this keyword to remove the subinterface ID from the
Interface-Id field.
The hostname and vrname keywords are a toggle; that is, specifying either hostname
or virtual router name turns off the other selection.
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To configure the relay agent option 82 information:
host1(config)# set dhcp relay options hostname
Preventing Option 82 Information from Being Stripped from Trusted Client Packets
You can configure DHCP relay or DHCP relay proxy to preserve option 82 information
for trusted clients. This ensures that DHCP relay and DHCP relay proxy prevent
option 82 information from being stripped off packets destined for a trusted client.
A trusted client has a giaddr value of 0. If DHCP relay is configured not to remove
option 82 and the giaddr field is 0, option 82 information remains in the packets.
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To prevent the option 82 information from being removed from packets destined
for a trusted client:
host1(config)# set dhcp relay preserve-trusted-client-option
Configuring Relay Agent Information Option (Option 82) Suboption Values
The DHCP relay agent information option (option 82) enables you to include additional
useful information in the client-originated DHCP packets that the DHCP relay forwards
to a DHCP server.
When the DHCP relay agent information option is enabled, the DHCP relay adds the
option 82 information to packets it receives from clients, then forwards the packets
to the DHCP server. The DHCP server uses the option 82 information to decide which
IP address to assign to the client—the DHCP server might also use information in
the option 82 field for additional purposes, such as determining which services to
grant to the client. The DHCP server sends its reply back to the DHCP relay, which
removes the option 82 information field from the message, and then forwards the
packet to the client.
The option 82 information is made up of a sequence of suboptions. JUNOSe software
supports the following DHCP relay agent information suboptions.
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Agent Circuit ID (suboption 1)—An ASCII string that identifies the interface on
which a client DHCP packet is received.
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Agent Remote ID (suboption 2)—An ASCII string assigned by the relay agent that
securely identifies the client.
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Vendor-Specific (suboption 9)—The JUNOSe software data field, which contains
the Internet Assigned Numbers Authority (IANA) enterprise number (4874) used
by JUNOSe software and either or both the layer 2 circuit ID and the user packet
class.
Configuring DHCP Relay and BOOTP Relay
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Chapter 20: Configuring DHCP Relay