ZyXEL Communications GS3700 Series Podręcznik Użytkownika Pobierz pdf (Strona 301)

Chapter 37 DHCP

GS3700/XGS3700 Series User’s Guide

301

information (such as the IP address and subnet mask) between a DHCP client and a DHCP server.

Once the DHCP client obtains an IP address and can connect to the network, network information

renewal is done between the DHCP client and the DHCP server without the help of the Switch.

The Switch can be configured as a global DHCP relay. This means that the Switch forwards all DHCP

requests from all domains to the same DHCP server. You can also configure the Switch to relay

DHCP information based on the VLAN membership of the DHCP clients.

37.4.1 DHCPv4 Relay Agent Information

The Switch can add information about the source of client DHCP requests that it relays to a DHCP

server by adding Relay Agent Information. This helps provide authentication about the source of

the requests. The DHCP server can then provide an IP address based on this information. Please

refer to RFC 3046 for more details.

The DHCP Relay Agent Information feature adds an Agent Information field (also known as the

Option 82 field) to DHCP requests. The Option 82 field is in the DHCP headers of client DHCP

request frames that the Switch relays to a DHCP server.

37.4.1.1 DHCPv4 Relay Agent Information Format

A DHCP Relay Agent Information option has the following format.

i1, i2 and iN are DHCP relay agent sub-options, which contain additional information about the

DHCP client. You need to define at least one sub-option.

37.4.1.2 Sub-Option Format

There are two types of sub-option: “Agent Circuit ID Sub-option” and “Agent Remote ID Sub-

option”. They have the following formats.

The 1 in the first field identifies this as an Agent Circuit ID sub-option and 2 identifies this as an

Agent Remote ID sub-option. The next field specifies the length of the field.

Table 151 DHCP Relay Agent Information Option Format

Code

(82)

Length

(N)

i1 i2

...

Table 152 DHCP Relay Agent Circuit ID Sub-option Format

SubOpt Code Length Value

(1 byte)

Slot ID, Port ID, VLAN ID, System Name or String

Table 153 DHCP Relay Agent Remote ID Sub-option Format

SubOpt Code Length Value

(1 byte)

MAC Address or String

1 2 ... 296 297 298 299 300 301 302 303 304 305 306 ... 415 416

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ZyXEL Communications GS3700 Series Podręcznik Użytkownika Strona 301