Cisco 500 series Administration Manual page 386

Configuring DHCP
Interactions Between DHCP Snooping, DHCP Relay and Option 82
Cisco 500 Series Stackable Managed Switch Administration Guide
DHCP Relay
VLAN with IP Address
Option 82 Relay – is sent
Insertion with Option 82
Enabled
Bridge – no
Option 82 is
sent
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
Packet is sent
Option 82
Insertion without Option
Disabled 82
DHCP Relay
VLAN without IP Address
Packet is sent Relay – is sent
with the with Option
original 82
Option 82
Bridge – no
Option 82 is
sent
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
23
Relay –
discards the
packet
Bridge –
Packet is sent
with the
original
Option 82
Packet arrives
with Option
82
Relay –
discards the
packet
Bridge –
Packet is sent
with the
original
Option 82
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