Configuring DHCP
Interactions Between DHCP Snooping, DHCP Relay and Option 82
Cisco 500 Series Stackable Managed Switch Administration Guide
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The following describes how DHCP Reply packets are handled when DHCP
Snooping is disabled:
DHCP Relay
VLAN with IP Address
DHCP Relay
VLAN without IP Address
Packet arrives
without
Option 82
Packet arrives
with Option
82
Packet arrives
without
Option 82
Packet arrives
with Option
82
Option 82
insertion
disabled
Packet will be
sent without
Option 82
Packet will be
sent with the
original
Option 82
Relay – will
discard
Option 82
Bridge –
Packet will be
sent without
Option 82
Relay –
1. If reply
originates in
switch, packet
will be sent
without
Option 82
2. If reply
does not
originate in
switch, packet
is discarded
Bridge –
Packet will be
sent with the
original
Option 82
Option 82
insertion
enabled
Packet will be
sent without
Option 82
Relay –
Packet will be
sent without
Option 82
Bridge –
Packet will be
sent with the
Option 82
Relay – will
discard
Option 82
Bridge –
Packet will be
sent without
Option 82
Relay –
Packet will be
sent without
Option 82
Bridge –
Packet will be
sent with the
Option 82