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58 Switching Configuration
Figure 3-4. DHCP Binding
The DHCP snooping component does not forward server messages since they are forwarded in hardware.
DHCP snooping forwards valid DHCP client messages received on un-trusted interfaces to all trusted
interfaces within the VLAN.
The binding's database includes the following information for each entry:
• Client MAC address
• Client IP address
• Time when client lease expires
•Client VLAN ID
•Client port
DHCP snooping can be configured on switching VLANs and routing VLANs. When a DHCP packet is
received on a routing VLAN, the DHCP snooping application applies its filtering rules and updates the
bindings database. If a client message passes filtering rules, the message is placed into the software
forwarding path where it may be processed by the DHCP relay agent or forwarded as an IP packet.
No
binding
Tentative
binding
Complete
binding
DISCOVER,
REQUEST
DISCOVER
DECLINE,
NACK
ACK
RELEASE,
NACK