DHCP Relay/DHCP Forwarding on HP ProCurve E5406zl

Enable DHCP Relay:
ProCurve (config)# dhcp-relay

Disable DHCP Relay:
ProCurve (config)# no dhcp-relay

Forward DHCP requests on VLAN 10 to 1.1.1.1 (DHCP server):
ProCurve# configure
ProCurve(config)# vlan 10 ip helper-address 1.1.1.1

To check ip-helper on VLAN 10:
ProCurve (config)# show ip helper-address vlan 10

Remove ip-helper on VLAN 10:
ProCurve (config)# vlan 10
ProCurve (vlan-10)# ip helper-address 1.1.1.1