On my local home network I have a Raspberry Pi. If I plug it directly into the router (Vigor2860n) I can connect to it with VNC, using my laptop. If the Pi is connected via its WiFi, the connection is refused, despite the Pi being able to connect to the web for updates etc.

I'm making the assumption that it's a router set up problem. Are there any FAQs or threads I should read that deal with this sort of problem?

Many thanks,

Keith Lockstone.

If the Pi connects OK via WiFi and works for everything except VNC (is that correct?), then I think the problem is at the Pi end. Is VNC bound to the WiFi adapter; i.e. is it actually listening for connections?

There's nothing you can configure on the 2860's firewall, that will distinguish between a LAN connected client and a WiFi connected one. About the only possible areas, would be related to VLANs or 'bound DHCP addresses', but if misconfigured, these would give general connectivity issues.

(I've used a variety of Pi's with the 2860n over the last 8 years or so).

I can ping the Pi via the cable connection but not when I disconnect the LAN. The Pi is still functioning as it then went on to contact my (external) web server.

The Pi's local IP is set in its config files - neither the LAN or WiFi MACs are bound to it.

klockstone wrote:
I can ping the Pi via the cable connection but not when I disconnect the LAN. The Pi is still functioning as it then went on to contact my (external) web server.

The Pi will have a different IP address on its WiFi adapter to that on its Ethernet port, so that's probably as expected. You should be able to see that 'other' IP address when connected locally to the Pi - or in the DHCP lease table.

The Pi's local IP is set in its config files - neither the LAN or WiFi MACs are bound to it.

I actually meant the binding of the VNC application. As in, lots of network-based apps let you choose which interface to use, though I don't know if VNC does (it's donkey's years since I last used it).

But if you've succeeded in configuring the Pi to use the same IP address on both its interfaces, then you'd have an ARP issue to deal with at the client end (unplugging the LAN cable would just mean the client holds the MAC address for an inaccessible IP address...)

Do you know what the Pi's WiFi IP address is? Can you SSH to it, for example?

Problem partly solved:

I was playing with an old Samsung laptop that was loaded with a variant of XUbuntu - full of programs for use by radio amateurs. I tried pinging the Pi and it worked. I then tried pinging from the router and that worked. Finally changed the SSID to the one shared by the Pi and the Samsung and the ping worked - plus I had VNC access.

So the question is: why can't the connection be made via different SSIDs?

PS There doesn't seem to be a problem if the Pi has one fixed IP and both LAN and WiFi paths are open - it seems to automatically choose the LAN and the router flags up the WiFi MAC but without an associated IP.

It never ceases to amaze me, what the linux hobbyists will get up to :wink:

https://forums.raspberrypi.com/viewtopic.php?t=192460

'Bonding' the two interfaces together, seems to be the ultimate solution.

My recommendation remains the same: Don't do it.

(There again, it's been 34 years since I did my TCP/IP course. It was held at a Birds-Eye/Walls site and I ate 15 Magnums that week. That's mainly what I remember )