Interactions Between Dhcp Snooping, Dhcp Relay And Option - Cisco SF500-24 Administration Manual

Configuring DHCP

Interactions Between DHCP Snooping, DHCP Relay and Option 82

Interactions Between DHCP Snooping, DHCP Relay and
Option 82
Cisco 500 Series Stackable Managed Switch Administration Guide
an IP address or if the switch is not a router (Layer 2 switch) then an external
router is needed.
DHCP Relay and only DHCP Relay relays DHCP messages to a DHCP server
The following tables describe how the switch behaves with various combinations
of DHCP Snooping, DHCP Relay and Option 82.
The following describes how DHCP request packets are handled when DHCP
Snooping is not enabled and DHCP Relay is 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
Enabled Option 82
Bridge – no
Option 82 will
be sent
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 – no
Option 82 will
be sent
19
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
350