Using an external DHCP Server (dhcp relay/dhcp forwarding)

Installing and Using OpenWrt Network and Wireless Configuration
3

Thank you psherman for your reply!

Sorry, my original post was perhaps a little light on details. As for IP subnetting:

  • ISP Router is the sole DHCP server in the network, but unfortunately can only handle one 255.255.255.0 subnet - in my case 192.168.0.1/24.
  • I have some static IPs assigned for certain MAC addresses, e.g.:
    • 192.168.0.9 is my NAS
    • 192.168.0.3 is assigned to the MAC address of my the WAN ethernet interface of my OpenWrt box
    • 192.168.201 and 202 are the IP cameras (ideally)

As you know, the trouble is the NAT layer at the WAN interface forces everything that is connected to the OpenWrt box to be on its own subnet, rather than the OpenWrt box forwarding/relaying DHCP queries of new OpenWrt hosts/clients on to the ISP DHCP server, which would then assign IP addresses.

As for your questions:

  1. I cannot remove my ISP router unfortunately.
  2. The ISP router does not have a bridge mode.
  3. The OpenWrt box is very 'lightweight', i.e. is nowhere near as powerful as the ISP box that we have, so moving the family on to it would be less than ideal.
  4. The ISP router does allow static IPv6 routes. Could you elaborate on your idea there?
  5. The ISP router does allow my to disable the DHCP server, which I assume would make it request an IP address from another detected DHCP server on the network, which could perhaps be my OpenWrt box?
  6. The bridge firewall looks interesting, I will need to read more into it and get back to you.
  7. Are you familiar with DHCP Forwarding/Relaying in dnsmasq?