Piste Basher wrote:

when I plugged the laptop into the Mesh Root AP903, I could not access IP addresses on the VLAN0 LAN1 (192.168.1.xx),

Sorry but I'm a bit confused - you say that your Mesh Root AP903 is wired to the 2926, but if you plug the laptop into it it does not see LAN 1? But surely the AP903 is simply acting as a basic switch in this scenario? I don't understand that.

Sorry, my previous post was slightly wrong. To clarify and to provide a bit more information.
I have the VLAN0 LAN1 (192.168.1.xx) with no VLAN tag VID set for my home network. I have VLAN1 LAN2 (192.168.2.xx) as a guest network with a specific VID tag.
The 2926 and both the AP903's are on the VLAN0 LAN1 (192.168.1.xx) subnet.
The Mesh Root is wired to the 2926.
When the laptop's network card was prompted to connect to the VID tag for VLAN1 LAN2 (192.168.2.xx) on both AP903's, the computer did see the 2926 on 192.168.1.xx, but could not see the AP903 on the same subnet or anything on the home network.
I was just a bit surprised that I could see the 2926 router from the VLAN1 LAN2 (192.168.2.xx) subnet as I have unchecked 'Permit untagged device in P1 to access router'.

Sorry, but I'm still puzzled. If I connect my laptop to my guest network - and check that it has an IP address of 192.168.2.10 - then I most definitely cannot "see" my router on 192.168.1.1, or indeed anything else on my main network. This is irrespective of the setting of "allow untagged device in P1 to access the router".

You don't have Inter-LAN routing enabled by any chance?

Piste Basher wrote:
Sorry, but I'm still puzzled. If I connect my laptop to my guest network - and check that it has an IP address of 192.168.2.10 - then I most definitely cannot "see" my router on 192.168.1.1, or indeed anything else on my main network. This is irrespective of the setting of "allow untagged device in P1 to access the router".

You don't have Inter-LAN routing enabled by any chance?

I do have Inter-LAN routing enabled. This is because I need computers on VLAN0 LAN1 (192.168.1.xx) to see and control devices on VLAN1 LAN2 (192.168.2.xx). Because of this, I also have a firewall data filter setup blocking data from VLAN1 LAN2 (192.168.2.xx) to VLAN0 LAN1 (192.168.1.xx). This seemed like the easiest way to deal with the requirement.

foggy69 wrote:
Unfortunately, the device I want to connect has no facility to change the settings for VLAN tags ID. If it is plugged directly into the 2926, it is quite happy to connect to whatever VLAN I set it too.

But presumably only on Port 1 of the 2926, with the "Permit untagged device in P1 to access router" ticked?

The LAN ports on the AP903 appear to just bridge all traffic through to the Wireless link, for the far end to sort out.
(Which begs the question: "Why even have a 'Bridge VLAN to Mesh' option at all?" - does it just apply to its Wifi?)

If you add my favourite little Netgear switch GS105Ev2 downstream of the AP903, it can do the job of tagging/untagging the traffic for you. (Normally less than £25 inc delivery, from Amazon).

OK so I have braved the cold of the garage once again to undertake a further test.

You don't say what the "device" is that you wish to connect, but you say that you can set it to connect to a specific VLAN so I am assuming that, like a PC network adapter, you can tell it to use a specific IP address and gateway address.

So I took my laptop out again and this time I told it to connect to 192.168.2.10, rather than "obtain an IP address automatically", and leaving the VLAN tag unset. On plugging into the AP903 node it obediently connected to the 192.168.2.x network.

I have of course piped all three of my VLANs to the mesh network in the router settings. As I suspected from my tests yesterday, all of the VLANS are present on the ethernet ports of the wirelessly connected AP903 in the garage - and I have now shown that it is not necessary to use VLAN tagging on the device if you are able to tell the device which VLAN to use.

So as I see it, if you can plug your device into the router and tell it which VLAN to connect to (assuming you have piped that VLAN to whichever port you're using) then there is no reason why you can't do the same on any of the wired or wireless AP903s in your system.

Unless I have completely misunderstood what your problem is, I can only think that there's something amiss with your settings somewhere along the line, but imho I don't think you can blame the AP903s.

Piste Basher wrote:
OK so I have braved the cold of the garage once again to undertake a further test.

You don't say what the "device" is that you wish to connect, but you say that you can set it to connect to a specific VLAN so I am assuming that, like a PC network adapter, you can tell it to use a specific IP address and gateway address.

Thank you for braving the cold for this.
The device is a Myenergi Hub, it is used to monitor power usage and control certain devices within the house.
There appears to be no way to access the network settings of the device, and the way I got it to connect to specific VLAN's was to use the 'Bind IP to MAC' setting or plugged it into ports on the 2926 that having been configured for VLAN1 LAN2 (192.168.2.xx).
I have contacted their technical support to ask for advice.