Reply To: IP Helper Hi all, Does anyone know if can add a IP helper on rt-ax86U? Trying to get PXE boot to work but its failing and I’ve seen that the alternative of…

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For reference. What is IP Helper ?

What is the difference between dhcp and IP helper-address ?

Using the IP helper-address command sets up a DHCP relay. DHCP only works on the LAN to which it is connected because it uses broadcast, which cannot cross a router. To remedy that situation, DHCP relay was created. It gives DHCP an option so that a router intercepts the DHCP client’s broadcast request, creates a unicast request to the DHCP server on a different LAN, and the DHCP server can give a unicast response to the router based on the DHCP option, that then passes on the DHCP response to the requesting DHCP client.

The key piece of this is that the Router sending the DHCP request on behalf of the client will unicast the request with a source address from the address space the client is in (the interface the relay/helper-address is configured on). This is ensures the DHCP server offers an IP from the correct scope.

IP Helper (I believe) was/is a Cisco based service.

Ref: https://networkengineering.stackexchange.com/questions/41376/how-ip-helper-address-works

 

In a completely sane world, madness is the only freedom (J.G.Ballard).

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