Cisco 350 Series Administration Manual page 382

IP Configuration
IPv4 Management and Interfaces
Cisco 350, 350X and 550X Series Managed Switches, Firmware Release 2.4, ver 0.4
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 is sent
Insertion without Option 82
Disabled
Option 82 Relay – is sent
Insertion with Option 82
Enabled
Bridge – Option
82 is added
(if port is trusted,
behaves as if
DHCP Snooping is
not enabled)
The following describes how DHCP Reply packets are handled when DHCP Snooping is
disabled:
DHCP Relay
VLAN with IP Address
Packet arrives
without Option
82
DHCP Relay
VLAN without IP Address
Packet arrives Packet arrives
with Option 82 without Option
82
Packet is sent Relay – inserts
with the Option 82
original Option
Bridge – no
82
Option 82 is
inserted
Packet is sent Relay – is sent
with the with Option 82
original Option
Bridge – Option
82
82 is inserted
(if port is
trusted, behaves
as if DHCP
Snooping is not
enabled)
DHCP Relay
VLAN without IP Address
Packet arrives Packet arrives
with Option 82 without Option
82
16
Packet arrives
with Option 82
Relay – discards
the packet
Bridge – Packet
is sent with the
original Option
82
Relay –discards
the packet
Bridge – Packet
is sent with the
original Option
82
Packet arrives
with Option 82
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