PowerConnect B-Series FCX Configuration Guide 1355
53-1002266-01
DHCP relay agent information (DHCP Option 82)
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As illustrated in Figure 178, the DHCP relay agent (the PowerConnect switch), inserts DHCP option
82 attributes when relaying a DHCP request packet to a DHCP server.
FIGURE 178 DHCP Option 82 attributes added to the DHCP packet
As illustrated in Figure 179, the PowerConnect switch deletes DHCP option 82 attributes before
forwarding a server reply packet back to a DHCP client.
FIGURE 179 DHCP Option 82 attributes removed from the DHCP packet
The DHCP option 82 insertion/deletion feature is available only when DHCP snooping is enabled
for the client/server ports.
Configuration notes
• DHCP snooping and DHCP option 82 are supported on a per-VLAN basis.
• DHCP option 82 follows the same configuration rules and limitations as for DHCP snooping.
For more information, refer to “Configuration notes and feature limitations” on page 1351.
DHCP Option 82 sub-options
The Dell implementation of DHCP Option 82 supports the following sub-options:
• Sub-Option 1 – Circuit ID
• Sub-Option 2 - Remote ID
• Sub-Option 6 – Subscriber ID
These sub-options are described in the following sections.
DHCP
Client
DHCP
Server
Trusted
Untrusted
DHCP
Snooping
DHCP Relay Agent
option
82
DHCP client
request packet
+
option 82
Switch
DHCP
Client
DHCP
Server
DHCP Server
reply packet
Trusted
Untrusted
DHCP
Snooping
option 82
DHCP Relay Agent
option
82
Switch
