H3C Technologies H3C WX3000E Series Wireless Switches - Manual (Page 264)

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Recording IP-to-MAC mappings of DHCP clients
DHCP snooping reads DHCP-REQUEST messages and DHCP-ACK messages from trusted ports to record
DHCP snooping entries, including MAC addresses of clients, IP addresses obtained by the clients, ports
that connect to DHCP clients, and VLANs to which the ports belong.
Ensuring DHCP clients to obtain IP addresses from authorized DHCP servers
If there is an unauthorized DHCP server on a network, DHCP clients may obtain invalid IP addresses and
network configuration parameters, and cannot normally communicate with other network devices. With
DHCP snooping, the ports of a device can be configured as trusted or untrusted, ensuring the clients to
obtain IP addresses from authorized DHCP servers.
• Trusted: A trusted port forwards DHCP messages normally.
• Untrusted: An untrusted port discards the DHCP-ACK or DHCP-OFFER messages received from any
DHCP server.
Configuring the DHCP server
Recommended configuration procedure
Step Remarks
1. Enabling DHCP
Required
Enable DHCP globally.
By default, global DHCP is disabled.
2. Creating a static address
pool for the DHCP server
Required to configure either of the two
IMPORTANT:
• If the DHCP server and DHCP clients are on the same subnet, make sure
the address pool is on the same network segment as the interface with the
DHCP server enabled; otherwise, the clients will fail to obtain IP
addresses.
• If a DHCP client obtains an IP address via a DHCP relay agent, an IP
address pool on the same network segment as the DHCP relay agent
interface must be configured; otherwise, the client will fail to obtain an IP
address.
3. Creating a dynamic
address pool for the DHCP
server
4. Enabling the DHCP server
on an interface
Optional
With the DHCP server enabled on an interface, upon receiving a client’s
request, the DHCP server will assign an IP address from its address pool to
the DHCP client.
With DHCP enabled, interfaces work in the DHCP server mode.
IMPORTANT:
• An interface cannot serve as both the DHCP server and the DHCP relay
agent. The latest configuration takes effect.
• The DHCP server works on interfaces with IP addresses manually
configured only.