BT Home Hub 5A as client over Ethernet

Hi guys, I'm using a BT Home Hub 5A with OpenWrt 18.06.2 r7676 connected via ethernet to my main ISP router (DGA4132, TIM, Italian ISP).

DGA4132 IP is and I've configured DNS in its webif using Google DNS, so every pc connected to it in DHCP uses Google DNS. BT Home Hub 5A is

Now, when I connect ethernet to BT Home Hub 5A, every computer connected to DGA4132 shows as DNS ipv4 and doesn't use Google DNS anymore.

How can I configure BT Home Hub 5A to fix this situation?

Thanks in advance for the reply!

Why would you want to do that? Once you have setup the router to use Google as upstream DNS, it will forward your local client requests to Google.

Assuming for some reason that you really need to do that, you could add a
list dhcp_option 'option:dns-server,'
to your "config dhcp 'lan'" section of /etc/config/dhcp and this should do the trick.

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The main reason I configured my ISP router with Google DNS is because I needed alternative DNS. Are you suggesting me to use different DNS? I could try Open DNS!

The real question I did (maybe I didn't explain myself well) is: why the main ISP uses correctly Google DNS when BT is not wired connected to main, while this doesn't happen when I connect BT to main ISP?

Hell, no: and are Google's own DNS servers.

Honestly, I thought I understood the first version but this one not so much :wink:

I assumed you connected the wan port of the BT to a client port of the router ISP. If this is not true, you have two DHCP servers active on the same LAN and that normally means trouble.

Did you asked me why I use Google DNS for what reason? In this way, I hope to underst and better your question! :slightly_smiling_face:

Ok, so I should deactivate DHCP in BT.

First explain how you have connected your router to the ISP router. From what port to what port.


Main ISP router have 4 ethernet ports. I used port 4 of main ISP router connected to a tp link 4 managed ports. Then one of the hub ports is connected to ethernet port 1 of the BT.

My best guess is that you currently have BTHH5A DHCP Server on. If you turn it off, things will work as expected.

I suggest using and as DNS instead of Google's.

And you should consider upgrading your BTHH5A to 19.07.3.


Ok, I'll change DNS on main router, too.

Is it safe to upgrade BT firmware?

No, I did not. I gave you an example that configures your DHCP server to send Google DNS server address directly to your lan clients, assuming this is what you want.

Yes, I meant on the main router, not BTHH5A.

For BTHH5A, you should just turn the DHCP off of you are using it as a switch.

I upgraded mine and don't have a problem.

On a different setup, you could turn your ISP router on a bridge mode, connect it to BTHH5A WAN port. That would make BTHH5A work as a router (and you would need the DHCP Server on for that).

I don't have this device here: is port 1 "wan" or just one of the lan ports?
If it is wan, then it should be ok.
If it is a normal lan port, then you indeed have 2 different DHCP servers fighting on the same network.

The port 1 is a lan port. So I have to disable DHCP on BT, I suppose.

Unfortunately my main ISP router doesn't support bridge mode, so I need to disable DHCP on BT and use it as a switch.

What's the safest way to upgrade BT firmware?

A lot depends on what you're trying to do, which is something you haven't really told us yet :slight_smile:
As far as the post title goes, "as a client" to me means "connecting the wan port of the BT to a lan port of the ISP router".
Another option would be using the BT as a dumb AP but that's a different scenario.

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Yes, you're right! I just have main ISP on the first floor of my house and bt on the second floor. I use bt to connect via LAN a couple of pc and consoles and have WiFi, too. So maybe using it as a switch, disabling DHCP, could be the best option to use.

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In that case what your trying to achieve is a dumb access point.

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Without knowing the name, I've already done a dumb access point method on it!

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