How to get internet access when connecting opnsense router to existing router?

[P195]

Hi All,

I'm trying to connect my OPNsense router to my existing ISP router so I can use my local PC to learn and configure OPNsense while still allowing the rest of my family to use the wireless functionality of the ISP router.

I've connected one of the LAN ports of the the ISP router to the WAN port of the OPNsense router and am able to access the GUI on 192.168.1.1.

When I was using the ISP router in bridge mode before, I had to use PPPoE for the WAN and input my broadband credentials which enabled internet access. When trying to configure this as a router behind a router (which isn't in bridge mode), should I be using DHCP, PPPoE or static IP for the WAN?

Should my network card in my PC be set to obtain IP automatically or do I need to specify a specific IP/subnet mask/gateway ?

Is there anything that I would need to change (or information I would need to know) in the GUI for the ISP router?

I've spent all day today trying to get internet access but to no avail. I'd be very grateful for any advice on what I need to do to get internet access to work when using OPNsense behind my ISP router when not bridged.

Thanks
P195

[Patrick M. Hausen]

Interfaces > WAN > Block private networks.

Uncheck that feature.

[P195]

Thank you for your response.

I have already unchecked "block private networks" and "block bogon networks" under Interfaces > WAN.

I followed this guide https://homenetworkguy.com/how-to/use-opnsense-router-behind-another-router/ (but not the optional bits at the bottom) but I still wasn't able to get internet access.

I wondered if it was because I needed to do something either in the ISP router config GUI, or on the PC network card TCP/IPv4 setup? Also I'm unsure if I should I be using DHCP, Static IPv4 or PPPoE for the WAN interface?

My ISP router is reached on 192.168.1.254. My OPNsense router is currently setup as IP 192.168.1.1.
Do I need to change the subnet of the LAN interface so it is not 192.168.1.XXX? Should I set it as something like 10.0.0.1 ?

Many Thanks!

[Patrick M. Hausen]

Default OPNsense installation, WAN connected to old router, LAN connected to PC - Internet should "just work".

Assuming:

- block private networks is disabled
- the old router does NOT use the network 192.168.1.0/24

If the second point is indeed the case you need to reconfigure the OPNsense LAN address and the DHCP server settings. But that should be all - no other tweaks necessary.

[P195]

Thanks.

So to clarify,

I need to setup the WAN interface to use DHCP, not static IPv4 as described in the linked guide?
I need to change the LAN address to something other than 192.168.1.XXX? something like 172.X.X.X or 10.X.X.X?
When you say reconfigure the DHCP server settings what do you mean? Like the IP range?

Sorry for the noobie questions!

[Patrick M. Hausen]

1. A newly installed OPNsense uses DHCP for WAN. Just plug in.

2. Yes, you would need to change LAN to e.g. 192.168.2.1/24. Then give your PC a static address in thst network and adjust Services > DHCPv4 > LAN to match that network.

Then switch your PC back to DHCP again.

[P195]

I appreciate your support. I'll have another go at it tonight armed with this information.

Cheers

Update: it worked

[cliffwilliams44]

Interfaces > WAN > Block private networks.

Uncheck that feature.

Yeah, I struggled with this for a whole day.

It would be nice if when you configure the wan interface it would detect it has a private IP and warns you to uncheck this option or prompt you to turn it off.

It would save newbies like me some headaches.