Simon Hobson dhcp1 at thehobsons.co.uk
Tue Jul 15 11:27:36 UTC 2008

At 12:53 +0200 15/7/08, Nathan Burgener wrote:
>I have 2 networks, which are connected over a VPN. In the network A, 
>there is a DHCP server.
>In network B I have the client. But all client address from source 
>192.168.3.x get a IP from network 172.18.1.x with NAT and then the 
>traffic goes through the VPN tunnel.
>On the router in network B I have an ip helper-address to the DHCP server.
>Now the server gets the Discover from the client with the following 
>Source IP
>Destination: Address from DHCP server
>Relay Agent IP Address:
>The DHCP server will now send back the offer. But the servers sends 
>it to and not to the address
>How can I change that?

Quick answer: Fix your network !
NAT == broken<period> and DHCP will not work in this setup.

You might be able to work around part of it by adding appropriate 
routing and/or nat rules to get the packets back to the relay agent, 
or by being creative with shared-network, but then the clients will 
not be able to renew their leases later and things will still break.

Can you remove the nat and make traffic routable between the server 
subnet and the 192.163.3.x subnet ?

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