Cisco SF500-24 Administration Manual page 361

Configuring DHCP
Interactions Between DHCP Snooping, DHCP Relay and Option 82
Cisco 500 Series Stackable Managed Switch Administration Guide
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
Option 82 Packet will be
insertion sent without
disabled Option 82
Option 82 Packet will be
insertion sent without
enabled Option 82
DHCP Relay
VLAN without IP Address
Packet arrives Packet arrives
with Option without
82 Option 82
Packet will be Relay – will
sent with the discard
original Option 82
Option 82
Bridge –
Packet will be
sent without
Option 82
Relay – Relay – will
Packet will be discard
sent without Option 82
Option 82
Bridge –
Bridge – Packet will be
Packet will be sent without
sent with the Option 82
Option 82
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Packet arrives
with Option
82
Relay –
1. If reply
originates in
switch, packet
will be sent
without
Option 82
2. If reply
does not
originate in
switch, packet
is discarded
Bridge –
Packet will be
sent with the
original
Option 82
Relay –
Packet will be
sent without
Option 82
Bridge –
Packet will be
sent with the
Option 82
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