Ip Helper Enable - Dell PowerEdge M420 Reference Manual

and DNS packets received on vlan 5 to 192.168.40.2,
relays SNMP traps (port 162) received on interface
vlan 6 to 192.168.23.1, and drops DHCP packets
received on vlan 6:
console#config
console(config)#ip helper-address 192.168.40.1 dhcp
console(config)#interface vlan 5
console(config-if-vlan5)#ip helper-address
192.168.40.2 dhcp
console(config-if-vlan5)#ip helper-address
192.168.40.2 domain
console(config-if-vlan5)#exit
console(config)#interface 2/6
console(config-if-vlan6)#ip helper-address
192.168.23.1 162
console(config-if-vlan6)#ip helper-address discard
dhcp

ip helper enable

Use the ip helper enable command to enable relay of UDP packets. To
disable relay of all UDP packets, use the "no" form of this command.
Syntax
ip helper enable
no ip helper enable
Default Configuration
IP helper is enabled by default.
Command Mode
Global Configuration mode.
909
IP Helper/DHCP Relay Commands