LevelOne GEL-1061 - Figure 299: Layer 3 DHCP Relay Service

Chapter 16 | IP Services
Dynamic Host Configuration Protocol
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Option 82 information contains information which can identify both the relay
agent and the interface through which the DHCP request was received:
◆ The DHCP Relay Information Option Remote ID (RID) is the access node
identifier – a string used to identify the switch to the DHCP server.
◆ The DHCP Relay Information Option Fields are the Option 82 circuit
identification fields (CID – including VLAN ID, stack unit, and port). These fields
identify the requesting device by indicating the interface through which the
relay agent received the request.
Figure 299: Layer 3 DHCP Relay Service
Command Usage
◆ You must specify the IP address for at least one active DHCP server. Otherwise,
the switch’s DHCP relay agent will not be able to forward client requests to a
DHCP server. Up to five DHCP servers can be specified in order of preference.
If any of the specified DHCP server addresses are not located in the same
network segment with this switch, specify the default router through which
this switch can reach other IP subnetworks (see “Configuring the IPv4 Default
Gateway” or “Configuring the IPv6 Default Gateway”).
◆ DHCP relay configuration will be disabled if an active DHCP server is detected
on the same network segment.
◆ DHCP Snooping Information Option 82 (see page 299) and DHCP Relay
Information Option 82 cannot both be enabled at the same time.
◆ DHCP request packets received by the switch are handled as follows:
■
If a DHCP relay server has been set on the switch, when the switch receives
a DHCP request packet without option 82 information from the
management VLAN or a non-management VLAN, it will add option 82 relay
information and the relay agent’s address to the DHCP request packet, and
then unicast it to the DHCP server.
■
If a DHCP relay server has been set on the switch, when the switch receives
a DHCP request packet with option 82 information from the management
Provides IP address
compatible with switch
segment to which client
is attached
DHCP
Server