Cisco SF500-24 Administration Manual page 316

IP Configuration
IPv4 Management and Interfaces
Cisco 500 Series Stackable Managed Switch Administration Guide Release 1.3
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
Disabled 82
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 Packet arrives
arrives with without
Option 82 Option 82
Packet is Relay – inserts
sent with the Option 82
original
Bridge – no
Option 82
Option 82 is
inserted
Packet is Relay – is sent
sent with the with Option 82
original
Bridge –
Option 82
Option 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 without
82 Option 82
17
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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