Same MAC address on two different HA devices - how?

klogg · August 10, 2018, 9:39am

The subject pretty much covers it.

I am setting up a second RPi with hassio for testing purposes but the second one will not complete the setup. I don’t get as far as the pretty HA preparation screen - just lots of text log messages and if it helps, the last one being :-

[ 110.073556] nf_conntrack: default automatic helper assignment has been turned off for security reasons and CT-based firewall rule not found. Use the iptables CT target to attach helpers instead.

The strange thing is that it shows as having the same MAC address as the first Pi. I have confirmed this by judicious plugging and unplugging of network cables . As well as looking on the router I have also checked using Fing as well as a small Windows network scanner.

How is it possible to have two devices show with the same MAC addresses when I know for a fact that they don’t (obviously?) because I have previously made a note of them?

Or have I missed something else?

Whatever the case it looks like until this is resolved I cannot get my second hassio Pi to start so any help or pointers would be much appreciated.

DavidFW1960 · August 10, 2018, 9:44am

Your router is assigning both Pi’s the same IP address???

klogg · August 10, 2018, 9:48am

Yes. But I have had them both attached to the network separately but how would explain them having the same MAC address?.

jimpower · August 10, 2018, 10:09am

It’s not possible for them to have the same layer 2 address. Did you change anything in your dhcp server to set your ip statically?

klogg · August 10, 2018, 10:24am

Yes I did.

RPi-1 was my original HA server set to static IP x.x.x.25. I was having some serious issues with HA so I set up RPi-2 to replace it giving it the same static IP x.x.x.25. (The issues were software related but I didn’t want to destroy the original HA server until I had a working replacement).

RPi-1 was ‘retired’ and until today was never again on the network. RPi-2 has been running HA ever since.

So, yes, both Pis have been assigned the same static IP which I know will cause problems if they both (try to) join the network at the same time.

But I thought that the router identified a device by MAC address and allocated the IP address, static or DHCP based on that?

What I don’t understand is even though there is an issue with IP addresses which know I need to sort out, why the two devices show as the same MAC address even when only one of them is attached to the network?

jimpower · August 10, 2018, 10:33am

Your router is probably still holding the dhcp lease for your old RPi, and this will cause you to not be able to access the new instance. I would delete the binding from your router have your new instance come up on its own dynamically assigned address and then once it has finished the hassio install assign it to your desired IP and reboot so it picks up the IP address.

klogg · August 10, 2018, 10:42am

Thanks I’ll give that a another look.
I say “another” because I have been poking around on my router thinking along those lines but my router is not as intuitive as it could. In fact it is not as anything as it could be. I am afraid it is a consumer BT SmartHub (Hub? yes. Smart? Not so much).

I have a feeling I may not get this resolved until I replace my router which I am about to pull the trigger on. I’m very close to going for a Ubiquiti Edgerouter X with an AP-Pro but am hesitant due to the simplicity of a mesh, Netgear Orbi or maybe Google…….

Yuran · August 10, 2018, 10:44am

I use a Netgear Orbi and has NEVER looked back. I have the router plus 1 indoor satellite and one outdoor. Never any problems and the router is SMART enough for all my needs

jimpower · August 10, 2018, 11:01am

Ubiquity or net gear are both more then capable consumer level products that will give a tad more functionality then what you’re using. In saying that you shouldn’t need to replace your router to resolve this issue worst case scenario is you wait out the routers lease time which is probably 24hrs and there should be no more conflict.

paul2nz · August 10, 2018, 11:17am

Hi had the same issue with 2 x pi and asus router. I treid setting manual ip address in router but no luck. I installed new image using etcher and setup a usb memory stick (as per instructions) with network configuration for hassOS as per doc, but changed the uuid and set a static ip. Plug in usb in pi and boot pi with new memory card. I am no professional but somehow it workes for me. Not sure if it was the different uuid or the static ip that made it work

github.com

home-assistant/operating-system/blob/dev/Documentation/network.md

# Network

HassOS uses NetworkManager to control the host network.

## Configure network

Only a manual configuration using NetworkManager connection files is supported. Without a configuration file, the device will use DHCP by default. These network connection files can be placed on a USB drive and imported to the host as described in [Configuration][configuration-usb].

## Configuration examples

You can read the [NetworkManager manual][nm-manual] or find many configuration examples across the internet. Keep in mind that the system is read-only. If you don't want the IP address to change on every boot, you should modify the UUID property to a generic [UUID4][uuid]. Inside the `\CONFIG\network\` directory on the USB drive or SD card, create a file called `my-network` and add the appropriate contents below:

### Default

A preinstalled connection profile is provided by default:

```ini
[connection]
id=my-network
uuid=f62bf7c2-e565-49ff-bbfc-a4cf791e6add

This file has been truncated. show original

klogg · August 10, 2018, 11:32am

@jimpower
Thanks but if they are both set to (the same) static IP in the router do they still have a lease? Also for my own benefit if for no other reason, can you understand why they might show as the same MAC address? If the answer is yes and it is very technical no need to explain(!) but it is really bugging me how that can happen.

As for replacing the router the driver is about house WiFi coverage as I currently have dead spots covered by an old D-Link router as an AP and it is just too flakey. I started off thinking I’d just get a quality AP to replace the D-Link but that grew into wanting to leave behind the BT Hub as much as possible i.e. only keeping it for its modem capabilities.

aidbish · August 10, 2018, 12:12pm

Where are they showing the same MAC address, on the pi or the router

paul2nz · August 10, 2018, 12:24pm

Was on the router for me.

klogg · August 10, 2018, 12:49pm

Router.
I can’t look at the MAC address for the second Pi because it won’t finish building the hassio install.

I might try installing Raspbian on it and see if that helps me sort this out because I don’t seem to be able to get my router to forget either Pi.

aidbish · August 10, 2018, 1:04pm

is there nothing in the router to delete the ip reservations

klogg · August 10, 2018, 1:14pm

Not by that name.
I can ‘delete’ devices that are not currently connected, e.g. here I can delete the Samsung TV but I did this for my Pi but when I plugged it back in it still had the wrong MAC address and was given the same static IP address again. Meaning I guess that it is not actually deleted else it should have got a DHCP address, yes?

zarthan · August 10, 2018, 2:11pm

You can change MAC addresses and every OS I have ever used has an easy way to make the change. I don’t know what install method you have used so it is just easier to say Google is your friend.

klogg · August 10, 2018, 2:23pm

Ok thanks, but aren’t MAC addresses hard coded into the hardware unless spoofed temporarily in software?

The Pi giving me problems (i.e. has the ‘wrong’ MAC address) is trying to boot off an SD card with a fresh hassio image which won’t complete it’s installation.

flamingm0e · August 10, 2018, 2:23pm

Even hassio/hassos?

zarthan · August 10, 2018, 2:43pm

MAC addresses are usually hard coded but they can be changed in the OS. I have experienced odd MAC changes on one of my Pis and have seen suggestions that Broadcom did not hard code MACs but relied on the boot code to establish one.