Help on how to use device only as DHCP server

Installing and Using OpenWrt
1

Hello to all. I am a new user, I just installed yesterday, trying to figure out how to use my router as a DHCP only.

The problem I want to solve:
My provider router has limited options, and only allows me to reserve only 16 IPs in order to set static IPs to my devices. Since I have a lot of IoT stuff, I need more.

What I hope I can do:
Use another router as a DHCP server.

To be specific:
Provider gave me a HUAWEI router. It has a subnet 192.168.10.x, with subnet mask 255.255.255.0. Router's IP is 192.168.10.254.
I have an archer C20, on which I have installed Open WRT. I want to connect it to the network, same subnet, and use that as a DHCP server, and keep the huawei as the default gateway. This is the best solution - if possible to apply -, since everything will be the same on my network.

Is that possible? If so, any guidelines on where to start would be much appreciated.

Thank you!

2

Are you able to disable the Huawei router's DHCP server? this is a requirement if you want to run another DHCP server on the same subnet.

3

Yes, that option is enabled on my Huawei.

4

Please confirm -- you have disabled the DHCP server on your Huawei. This means that a computer that is expecting an address via DHCP will not be able to get an address right now.

5

Yes, I have tried it and I can disable it.

6

Ok... great.

So what you need to do is:

  • disable the DHCP server on your huawei router
  • Set the LAN address of your openwrt router to an address in the same subnet as your main router (i.e. 192.168.10.x -- x may be anything between 1-253 in your case).
  • add a dns server to the lan interface of your OpenWrt router -- this can be your huawei router (192.168.10.254) or a public DNS like 8.8.8.8 or 1.1.1.1 etc.
  • Add dhcp option 3 (which defines the gateway address to be sent): 3,192.168.10.254
  • Optionally add dhcp option 6 (for DNS) if you want the OpenWrt router to advertise a DNS server other than itself.
2 Likes
7

Thank you very much for your time. Much appreciated.
I will give it a try tomorrow, and get back with the results.