Cisco SF500-24 Administration Manual page 360

Configuring DHCP
Interactions Between DHCP Snooping, DHCP Relay and Option 82
Cisco 500 Series Stackable Managed Switch Administration Guide
The following describes how DHCP request packets are handled when both
DHCP Snooping and DHCP Relay are enabled:
DHCP Relay
VLAN with IP Address
Packet arrives
without Option
82
Option 82 Packet will be
Insertion sent without
Disabled Option 82
Option 82 Relay – will be
Insertion sent with Option
Enabled 82
Bridge – Option
82 will be added
(if port is trusted,
behaves as if
DHCP Snooping
is not enabled)
DHCP Relay
VLAN without IP Address
Packet arrives Packet arrives
with Option without
82 Option 82
Packet will be Relay – will
sent with the insert Option
original 82
Option 82
Bridge – no
Option 82 will
be inserted
Packet will be Relay – will be
sent with the sent with
original Option 82
Option 82
Bridge –
Option 82 will
be inserted
(if port is
trusted,
behaves as if
DHCP
Snooping is
not enabled)
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Packet arrives
with Option
82
Relay – will
discard the
packet
Bridge –
Packet will be
sent with the
original
Option 82
Relay – will
discard the
packet
Bridge –
Packet will be
sent with the
original
Option 82
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