User manual

xStack DES-3800 Series Layer 3 Stackable Fast Ethernet Managed Switch
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Figure 8- 40. DHCP/ BOOTP Relay Global Settings window
The following fields can be set:
Parameter Description
Relay State
This field can be toggled between Enabled and Disabled using the pull-down menu.
It is used to enable or disable the DHCP/BOOTP Relay service on the Switch. The
default is Disabled
Relay Hops Count
Limit (1-16)
This field allows an entry between 1 and 16 to define the maximum number of router
hops DHCP/BOOTP messages can be forwarded across. The default hop count is 4.
Relay Time Threshold
(0-65535)
Allows an entry between 0 and 65535 seconds, and defines the maximum time limit
for routing a DHCP/BOOTP packet. If a value of 0 is entered, the Switch will not
process the value in the seconds field of the BOOTP or DHCP packet. If a non-zero
value is entered, the Switch will use that value, along with the hop count to determine
whether to forward a given BOOTP or DHCP packet.
DHCP Agent
Information Option 82
State
This field can be toggled between Enabled and Disabled using the pull-down menu.
It is used to enable or disable the DHCP Agent Information Option 82 on the Switch.
The default is Disabled.
Enabled –When this field is toggled to Enabled the relay agent will insert and remove
DHCP relay information (option 82 field) in messages between DHCP servers and
clients. When the relay agent receives the DHCP request, it adds the option 82
information, and the IP address of the relay agent (if the relay agent is configured), to
the packet. Once the option 82 information has been added to the packet it is sent on
to the DHCP server. When the DHCP server receives the packet, if the server is
capable of option 82, it can implement policies like restricting the number of IP
addresses that can be assigned to a single remote ID or circuit ID. Then the DHCP
server echoes the option 82 field in the DHCP reply. The DHCP server unicasts the
reply to the back to the relay agent if the request was relayed to the server by the
relay agent. The switch verifies that it originally inserted the option 82 data. Finally,
the relay agent removes the option 82 field and forwards the packet to the switch port
that connects to the DHCP client that sent the DHCP request.
Disabled- If the field is toggled to Disabled the relay agent will not insert and remove
DHCP relay information (option 82 field) in messages between DHCP servers and
clients, and the check and policy settings will have no effect.
DHCP Agent
Information O
p
tion 82
This field can be toggled between Enabled and Disabled using the pull-down menu.
It is used to enable or disable the Switches abilit
y
to check the validit
y
of the
p
acket’s