Application of trusted and untrusted ports
Configure ports facing the DHCP server as trusted ports, and configure other ports as untrusted ports.
As shown in Figure 29, configure the DHCP snooping device's port that is connected to the DHCP server as a trusted port. The trusted port forwards response messages from the DHCP server to the client. The untrusted port connected to the unauthorized DHCP server discards incoming DHCP response messages.
Figure 29: Trusted and untrusted ports
In a cascaded network as shown in Figure 30, configure the DHCP snooping devices' ports facing the DHCP server as trusted ports. To save system resources, you can enable only the untrusted ports directly connected to the DHCP clients to record DHCP snooping entries.
Figure 30: Trusted and untrusted ports in a cascaded network
