HP 1920 Gigabit Ethernet Switch Series User Manual page 320

Figure 283 Trusted and untrusted ports
In a cascaded network as shown in
connected to other DHCP snooping devices as trusted ports. To save system resources, you can disable
the untrusted ports that are not directly connected to DHCP clients from generating DHCP snooping
entries.
Figure 284 Trusted and untrusted ports in a cascaded network
Table 98 describes roles of the ports shown in
Table 98 Roles of ports
Device Untrusted port
GigabitEthernet
Switch A
1/0/1
Figure 284, configure each DHCP snooping device's ports
Figure 284.
Trusted port disabled from
recording binding entries
GigabitEthernet 1/0/3
307
Trusted port enabled to
record binding entries
GigabitEthernet 1/0/2