Dhcp Snooping Configuration; Dhcp Snooping Overview; Functions Of Dhcp Snooping - HP V1910 User Manual

DHCP snooping configuration

NOTE:
A DHCP snooping enabled device does not work if it is between the DHCP relay agent and DHCP
server, and it can work when it is between the DHCP client and relay agent or between the DHCP client
and server.
HP recommends you not to to enable the DHCP client, BOOTP client, and DHCP snooping on the same
device. Otherwise, DHCP snooping entries may fail to be generated, or the BOOTP client/DHCP client
may fail to obtain an IP address.

DHCP snooping overview

Functions of DHCP snooping

As a DHCP security feature, DHCP snooping can implement the following:
Table 85 Recording IP-to-MAC mappings of DHCP clients
Table 86 Ensuring DHCP clients to obtain IP addresses from authorized DHCP servers
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.
288