User`s manual

PT-7728 User’s Manual Featured Functions
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Configuring Set Device IP
Desired IP Address
Setting Description Factory Default
IP Address Set the desired IP of connected devices. None
Configuring DHCP Relay Agent
The DHCP Relay Agent makes it possible for DHCP broadcast messages to be sent over routers.
The DHCP Relay Agent enables DHCP clients to obtain IP addresses from a DHCP server on a
remote subnet, or those that are not located on the local subnet.
DHCP Option 82
Option 82 is used by the relay agent to insert additional information into the client’s DHCP
request. The Relay Agent Information option is inserted by the DHCP relay agent when
forwarding client-originated DHCP packets to a DHCP server. Servers recognize the Relay Agent
Information option and use the Information to implement IP address to the Client.
When Option 82 is enabled on the switch, a subscriber device is identified by the switch port
through which it connects to the network (in addition to its MAC address). Multiple hosts on the
subscriber LAN can be connected to the same port on the access switch and are uniquely
identified.
The Option 82 information contains 2 sub-options: Circuit ID and Remote ID, which define the
relationship between End Device IP and the DHCP option 82 server. The “Circuit ID” is a 4-bytes
number generated by Ethernet switch by the combination of physical port number and VLAN ID.
The format of the “Circuit ID” is as described below:
FF–VV–VV–PP
Where the first byte “FF” is fixed to “01”, the second and the third byte “VV-VV” is formed by
the port VLAN ID in hex, and the last byte “PP” is formed by the port number in hex. For
example,
01–00–0F–03 is the “Circuit ID” of port number 3 with port VLAN ID 15.
The “Remote ID” is to identify the relay agent itself. It can be one of the following types: