Configuration Guide DHCP Snooping Configuration
DHCP Snooping Configuration
Overview
DHCP
The DHCP protocol is widely used to dynamically allocate the recycled network resources, for
example, IP address. A typical IP acquisition process using DHCP is shown below:
The DHCP Client sends a DHCP DISCOVER broadcast packet to the DHCP Server. The Client
will send the DHCP DISCOVER again if it does not receive a response from the server within a
specified time.
After the DHCP Server receives the DHCP DISCOVER packet, it allocates resources to the
Client, for example, IP address according to the appropriate policy, and sends the DHCP
OFFER packet.
After receiving the DHCP OFFER packet, the DHCP Client sends a DHCP REQUEST packet
to obtain the server lease.
After receiving the DHCP REQUEST packet, the server verifies whether the resources are
available. If so, it sends a DHCP ACK packet. If not, it sends a DHCP NAK packet. Upon
receiving the DHCP ACK packet, the DHCP Client starts to use the resources assigned by the
server in condition that the ARP verification resources are available. If it receives the DHCP
NAK packet, the DHCP Client will send the DHCP DISCOVER packet again.
DHCP Snooping
DHCP Snooping monitors users by snooping the packets exchanged between the clients and
the server. DHCP Snooping can filter DHCP packets and illegal servers by proper configuration.
Some terms and functions used in DHCP Snooping are explained below:
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