Relay agent option (option 82) – H3C Technologies H3C WX3000E Series Wireless Switches User Manual

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shows the format of the value field of the PXE server address sub-option. The value of the

PXE server type can only be 0. The server number field indicates the number of PXE servers
contained in the sub-option. The server IP addresses field contains the IP addresses of the PXE

servers.

Figure 12 Format of the value field of the PXE server address sub-option

Relay agent option (Option 82)

Option 82 is the relay agent option in the option field of the DHCP message. It records the location

information of the DHCP client. When a DHCP relay agent or DHCP snooping device receives a client’s

request, it adds Option 82 to the request message and sends it to the server.
The administrator can locate the DHCP client to further implement security control and accounting. The

Option 82 supporting server can also use such information to define individual assignment policies of IP

address and other parameters for the clients.
Option 82 involves at most 255 sub-options. At least one sub-option must be defined. The DHCP relay
agent supports two sub-options: sub-option 1 (Circuit ID) and sub-option 2 (Remote ID).
Option 82 has no unified definition. Its padding formats vary with vendors.
There are two methods for configuring Option 82:

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User-defined method: Manually specify the content of Option 82.

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Non-user-defined method: Pad Option 82 in the default normal or verbose format.

If you choose the second method, you can specify the code type for the sub-options as ASCII or HEX.

Normal padding format

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Sub-option 1: Padded with the VLAN ID and interface number of the interface that received the
client’s request. The value of the sub-option type is 1, and that of the circuit ID type is 0.

Figure 13 Sub-option 1 in normal padding format

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Sub-option 2: Padded with the MAC address of the DHCP relay agent interface or the MAC
address of the DHCP snooping device that received the client’s request. The value of the sub-option
type is 2, and that of the remote ID type is 0.

This manual is related to the following products:

H3C WX5500E Series Access Controllers H3C WX3500E Series Access Controllers H3C WX2500E Series Access Controllers H3C WX6000 Series Access Controllers H3C WX5000 Series Access Controllers H3C LSWM1WCM10 Access Controller Module H3C LSUM3WCMD0 Access Controller Module H3C LSUM1WCME0 Access Controller Module H3C LSWM1WCM20 Access Controller Module H3C LSQM1WCMB0 Access Controller Module H3C LSRM1WCM2A1 Access Controller Module H3C LSBM1WCM2A0 Access Controller Module H3C WA3600 Series Access Points H3C WA2600 Series WLAN Access Points