DHCP snooping requires to be enabled globally before it will function correctly. If it is not enabled globally, even if enabled on VLAN interfaces, DHCP snooping will not work.

Enabling authorized DHCP servers (A) or trusted interfaces (B) is necessary but only after global enabling.

Enabling DHCP snooping on VLAN (C) is not sufficient without global enablement.

Therefore, enabling DHCP snooping globally is the first step to activate the feature.

ArubaOS-CX DHCP Snooping Configuration Guide

HPE Aruba Networking Security Best Practices

Aruba DHCP Snooping Troubleshooting Documentation