DHCP / IP Issues with Sky Broadband (UK FTTC DSL) Hub

[n_sonic]

Hello all.

Hoping you might be able to advise me on this issue please?

I recently received an updated modem/router from my broadband provider. It was supposedly the newer/better model and it should have been a simple swap out (followed by a couple of static IP/route tweaks).

My set up is super simple really.

The modem/router handles the WAN connection and provides DHCP via the LAN side. An Orbi RBR40 (in AP mode using DHCP to get an address) is connected via its "Internet" port to the modem/router and then the rest of the network is then provided via a number of connected satellites.

The above all worked fine until I swapped out the modem/router.

On it's own, the new modem/router (with it's wi-fi off) dishes out 192.168.0.x addresses and a "router" address of192.168.0.1 via its ethernet ports.

However, the moment the Orbi is connected to this new modem/router - everything starts getting 192.168.1.x addresses a "router" address of 192.168.0.250. This causes all internet connectivity to fail and neither the modem/router or Orbi are accessible via their browser-based admin interfaces anymore.

So simply put, the DHCP allocation works fine when the Orbi isn't connected and falls apart when it is connected. Connecting the Orbi to the old modem/router is fine and all devices start getting the correct 0.x addresses (and the correct router address) again.

If you have any suggestions at all, that would be amazing. Thank you!

[FURRYe38]

What Firmware version is currently loaded?

Be sure your RBR is is AP mode:

Disable all wifi radios on the modem and connect the Orbi router to the modem, configure AP mode on the Orbi router. https://kb.netgear.com/31218/How-do-I-configure-my-Orbi-router-to-act-as-an-access-point and https://www.youtube.com/watch?v=H7LOcJ8GdDo&app=desktop

Try setting a static IP address of 192.168.0.50 on the RBR for AP mode.

[n_sonic]

Hi there, thanks for the reply. Answers below...

"What Firmware version is currently loaded?"

I observed this behaviour whilst running 2.5.1.16 on the RBR40. I've upgraded to 2.6.2.104 today, but haven't had the time to try it out again.

"Be sure your RBR is is AP mode:"

I had already enabled this. I needed it in my previous set up to prevent double NAT issues from stopping external access to my Plex server.

"Disable all wifi radios on the modem and connect the Orbi router to the modem, configure AP mode on the Orbi router. https://kb.netgear.com/31218/How-do-I-configure-my-Orbi-router-to-act-as-an-access-point and https://www.youtube.com/watch?v=H7LOcJ8GdDo&app=desktop"

Already done. First thing I did was turn off the wi-fi on the modem/router.

"Try setting a static IP address of 192.168.0.50 on the RBR for AP mode."

Already tried this as well unfortunately. Setting a 192.168.0.X device on the Orbi didn't seem to make any difference. The DHCP just kept on assigning 1.x addresses.

Thanks again for the response 🙂

[FURRYe38]

Sounds like the RBR isn't fully in AP mode if you seeing .1.# coming thru or your main host router isn't working correctly. 

Try a factory reset on the RBR and setup from scratch. Do this with out the RBR connected to the host router. Get the RBR configured for wifi SSID and PW, then setup AP mode on the RBR. Give a static IP address that is in the range of what your using on the host router. Make sure that the static IP address is out side of the host routers default IP address pool aswell. Should not be with in it. 

[CrimpOn]

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@n_sonic wrote:

On it's own, the new modem/router (with it's wi-fi off) dishes out 192.168.0.x addresses and a "router" address of192.168.0.1 via its ethernet ports.

However, the moment the Orbi is connected to this new modem/router - everything starts getting 192.168.1.x addresses a "router" address of 192.168.0.250. This causes all internet connectivity to fail and neither the modem/router or Orbi are accessible via their browser-based admin interfaces anymore.

---

This happens when anything is connected to the new router, or just when the Orbi is connected?

The broadband supplier has no suggestions?

[n_sonic]

Good question. I've only tried plugging the Orbi in so far, so I can't answer that. I have a Hue hub and a Homebridge that I can try to see if it causes similar behaviour.

I've not reached out to the broadband supplier yet. I've been holding off, hoping to get some ideas from the support community first 🙂

I will try a couple of the other suggestions (static IP outside the DHCP range) and then try a full factory reset.

[CrimpOn]

Can you explain how you discovered the changing IP assignments?

Ordinarily, the first recommendation is to connect a PC directly to the modem/router with an ethernet cable and verify that "it works".

(I was thrown by the statement that the modem/router's WiFi is off.)

I would want to log into the modem/router and look at their version of Attached Devices to see what it reports about everything connected and its own LAN IP address.

[n_sonic]

"Can you explain how you discovered the changing IP assignments? Ordinarily, the first recommendation is to connect a PC directly to the modem/router with an ethernet cable and verify that "it works". (I was thrown by the statement that the modem/router's WiFi is off.)"

Very happy to 🙂

So, with the Orbi disconnected and wi-fi turned off on the modem/router, I connected a MacBook Pro (wi-fi off) to it directly via ethernet.

When it was just the laptop connected to the modem/router - it was getting the correct 0.x address and the right router address.

I then disconnected the laptop and re-connected the Orbi to the modem/router and gave it a moment to do its thing.

Then I did three more tests with the MacBook Pro.

The first test was with wi-fi off on the MBP. I connected it via ethernet into the modem/router and observed that it was now getting the 1.x address and the wrong router address.

The second test was with wi-fi off again on the MBP. I connected the MBP to the Orbi via ethernet. Again, 1.x addresses and the wrong router address was being assigned. 

The final test was to unplug the MBP ethernet and then connect it to the Orbi via wi-fi. Again, the 1.x address and wrong router address was assigned.

So, long story short - as soon as the Orbi was plugged in to the modem/router - everything starts getting 1.x addresses and the wrong router address (no matter where it's connected or how...)

"I would want to log into the modem/router and look at their version of Attached Devices to see what it reports about everything connected and its own LAN IP address."

Great idea. I'll do some more testing tomorrow (as I've got some updated firmware now) and will check what it says.

Thanks again!

[n_sonic]

Hello

I solved this eventually and I thought I'd follow up just in case it helps others with a similar issue.

The solution was simple in the end.

1. I restricted the DHCP address range on the modem/router to 192.168.0.2 - 192.168.0.249.

2. I set a fixed IP address (and subnet mask and DNS server) on the Orbi (outside the above range).

After that, it all started working perfectly and the network has been rock solid all weekend. (Although, I am now seeing some increased satellite disconnects, but this may be the new FW?)

I shouldn't really have had to debug this or configure the settings like this, but it seems to have been worth it as the network is more stable under load with the new modem/router!