Cisco Catalyst Switch – DHCP helper addresses
These instructions allow you to enable DHCP helper addresses to allow forwarding of UDP broadcasts including bootp and DHCP.
- Connect to the switch using Putty or your preferred method of CLI
- Run the command “show ip interface” and look for the line that says “Helper address is XXX.XXX.XXX.XXX” It may say “Helper address is not set”
Make sure you’re looking at the correct line for the interface you’re interested in checking.
**If you already know what interface you want to see you can specify, for example, for vlan 4: Run “show ip int vlan 4”
To set the helper address
- Run “configure terminal“
- Run “interface X” where X is the type and number of the interface to configure, for example to set the DHCP helper address for vlan 4 you would type “interface vlan 4”
- Run “ip helper-address X” where X is the address of the network or a specific server IP. Using the network address allows other DHCP servers to respond in case one is down.
Bonus points: To change the name of a VLAN:
“vlan vlan-id” where vlan-id is the id of the vlan to edit or create
“name X” where X is the new name