Communication between devices on the LAN

[Peter-123]

Folks, I have a Vodafone Fibre (THG3000) router and all devices using it connect to the Internet and work well. However, these devices struggle to connect to each other, even though they are on the same LAN.

When I logon to the router I can ping all the devices and all the devices can ping the router.

However, when I use a device I can wait maybe up to 15 minutes pinging (from the device) to other devices before I get a successful ping. If I reboot the router the devices can ping each other pretty much straight away.

There is nothing special about my setup. Software on all devices, including router, are up to date and all devices use IPv4. Not sure it is important but - Sharing is enabled, uPnP and Device Fingerprinting are enabled.

Anyone any ideas? Can't help but think it is a software bug on the router, this wasn't a problem with the Sky router.

[Cynric]

@Peter-123 How many devices?

If you can, turn off uPNP because it's a security risk.

Look at the DHCP settings and see what timeout is set. Try different values, perhaps 24 hours in the first attempt. I'm concerned that all the DHCP sessions may be used and this is why the router reset is helping. Are there more devices than addresses in the DHCP range.

Turn off IPv6.

See how you get on with these ideas.

[Peter-123]

Thanks for the reply Cynric, it was certainly worth checking.

I did turn off uPNP and IPv6. The DHCP range is from 192.168.1.2 - 192.168.1.255 and there are only ever about half a dozen devices connected at any one time. I played about with the DHCP timeout but none of this has made any difference.

Dare say I should have mentioned that all my devices are all Linux/Android based. I will try Microsoft/Apple devices when I can get my hands on them though I find it hard to think this will make a difference. I will post a note if I can identify anything helpful.

Thanks again.

[Cynric]

@Peter-123 Try changing the DHCP range to 2 to 254 please, the 255 one is reserved if I remember correctly.

Have you tried with fingerprinting off? Have you got any managed switches on the LAN?

I'm a *nix user as well 👍

[Peter-123]

Oops sorry, I should have said the DHCP range was  - 192.168.1.2 - 192.168.1.199.

I have turned off Fingerprinting, applied the settings and restarted the router. Unfortunately it has made no difference.

There are no switches on the LAN.  I mainly try to connect to a Raspberry PI and it makes no difference if I disable the firewall on it or not.

Unfortunately (in this case at least) I don't have any Microsoft or Apple devices around to check it they make a difference - I will need to wait until my nephews or nieces are about. I will keep in touch if I can add anything useful.

[Cynric]

@Peter-123 Are your Pis using WiFi as there's talk on GitHub about a problem with wpa_supplicant.

[Peter-123]

@Cynric Sorry for the delay getting back.

My Pis are using WiFi. (Not sure it is relevant but I have setup a static IP address on the PIs).

I have just noticed that when I connect my Pis to the router using a UTP cable I can connect to the Pi just fine from any other device!  Looks like you are right. 

[Cynric]

@Peter-123 My Pi collection are all wired, but that is not because I had WiFi issues like your, it was just a case of speed for me. However I am not using a VF router which could also be a reason why I haven't seen the same problem.

Just for reference, my builds are;

500 and 5B - Bookworm, kernel 6.6.62+rpt-rpi-2712

3B and 2B - Bullseye, kernel 6.1.21-v7+