ZyXEL Communications ES-2108, User Manual, Page: 190 / 284

Chapter 25 DHCP
ES-2108 Series User’s Guide
190
Figure 109 IP Application > DHCP
The following table describes the labels in this screen.
25.3 DHCP Relay
Configure DHCP relay on the Switch if the DHCP clients and the DHCP server are not in the
same broadcast domain. During the initial IP address leasing, the Switch helps to relay
network 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.
25.3.1 DHCP 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 to the Option
82 field. The Option 82 field is in the DHCP headers of client DHCP request frames that the
Switch relays to a DHCP server.
Relay Agent Information can include the System Name of the Switch if you select this
option. You can change the System Name in Basic Settings > General Setup .
The following describes the DHCP relay information that the Switch sends to the DHCP
server:
Table 69 IP Application > DHCP
LABEL DESCRIPTION
Relay Mode This field displays:
•
None - if the Switch is not configured as a DHCP relay agent.
• Global - if the Switch is configured as a DHCP relay agent only.
• VLAN - followed by a VLAN ID if it is configured as a relay agent for specific
VLAN(s).
Table 70 Relay Agent Information
FIELD LABELS DESCRIPTION
Slot ID (1 byte) This value is always 0 for stand-alone switches.
Port ID (1 byte) This is the port that the DHCP client is connected to.