Configuring DHCP
Interactions Between DHCP Snooping, DHCP Relay and Option 82
Cisco 500 Series Stackable Managed Switch Administration Guide
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an IP address or if the switch is not a router (Layer 2 switch) then an external
router is needed.
DHCP Relay and only DHCP Relay relays DHCP messages to a DHCP server
Interactions Between DHCP Snooping, DHCP Relay and
Option 82
The following tables describe how the switch behaves with various combinations
of DHCP Snooping, DHCP Relay and Option 82.
The following describes how DHCP request packets are handled when DHCP
Snooping is not enabled and DHCP Relay is 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 – no
Option 82 will
be sent
Packet will be
sent with the
original
Option 82
Relay – will be
sent with
Option 82
Bridge – no
Option 82 will
be sent
Relay – will
discard the
packet
Bridge –
Packet will be
sent with the
original
Option 82