IP helper adress

[klaasth]

What is the correct way to configure an IP helper adress in OPNsense?

We are using WDS+MDT for imaging our computers. The WDS server is on VLAN 1, computer clients are on other VLAN's. Microsoft advices to use IP helper adress instead of DHCP options to make imaging possible across VLANs
Our setup DHCP: each VLAN has its DHCP server running in OPNsense.

Kind regards

[mimugmail]

In DHCP there is a sub menu "Relay", it's ip helper.

[hbc]

As soon as any DHCP server in opnsense is enabled, no matter which interface, DHCP relay won't work. Maybe this (s|c)ould be fixed sometimes.

But in which way does ip-helper make any difference to dhcp server? The result is the same. DHCP server provides ip and options, ip-helper just relays request to DHCP server that provides ip and options.

The only difference is that if your DHCP server is not connected directly via interface to your subnets/VLANs, an ip-helper on a layer 3 routing devices relays/forwards the requests between clients and server.

In your case, OPNsense is the DHCP server and connected to every layer 3 network directly.

[EasyGoing1]

As soon as any DHCP server in opnsense is enabled, no matter which interface, DHCP relay won't work. Maybe this (s|c)ould be fixed sometimes.

But in which way does ip-helper make any difference to dhcp server? The result is the same. DHCP server provides ip and options, ip-helper just relays request to DHCP server that provides ip and options.

The only difference is that if your DHCP server is not connected directly via interface to your subnets/VLANs, an ip-helper on a layer 3 routing devices relays/forwards the requests between clients and server.

In your case, OPNsense is the DHCP server and connected to every layer 3 network directly.

ip-helper is essential when you have a DHCP server and you have VLANs because the ip-helper component in the DHCP relay server tags the DHCP requests with VLAN Ids so that the DHCP server knows which IP pool to assign an address from. IP-Helper is an option in a DHCP relay service but is not always necessary.