Configuring DHCP
Interactions Between DHCP Snooping, DHCP Relay and Option 82
Cisco 500 Series Stackable Managed Switch Administration Guide
351
19
The following describes how DHCP request packets are handled when both
DHCP Snooping and DHCP Relay are enabled:
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
insert Option
82
Bridge – no
Option 82 will
be inserted
Relay – will
discard the
packet
Bridge –
Packet will be
sent with the
original
Option 82
Option 82
Insertion
Enabled
Relay – will be
sent with Option
82
Bridge – Option
82 will be added
(if port is trusted,
behaves as if
DHCP Snooping
is not enabled)
Packet will be
sent with the
original
Option 82
Relay – will be
sent with
Option 82
Bridge –
Option 82 will
be inserted
(if port is
trusted,
behaves as if
DHCP
Snooping is
not enabled)
Relay – will
discard the
packet
Bridge –
Packet will be
sent with the
original
Option 82