Bridge Mode if going through PoE Switch?

At the moment I have an outdoor 4G modem/router in full router mode to my PoE Switch (unmanaged Netgear GS116LP) with some wired devices and also my ASUS AC86U as an Access Point for my wireless devices.

Shortly my modem provider will be releasing a new firmware that will enable Bridge or Modem Only mode on its device and my ASUS router is a much more capable device to handle DHCP, QoS and similar.

Given that it needs feeding from the PoE Switch, can I set the 4G modem/router to Modem Only, have it get its power from the PoE Switch, go through to the ASUS AC86U in full router mode but still access other wired devices from the Switch?

Does that make sense?

You would have to attach the Wan and the Lan ports of the Asus router to the same switch. It might work and I don't think it would cause any harm to try. You can buy small cheap PoE switches on ebay.

I already have a PoE switch (Netgear GS116). Would I need to do anything special with addresses on the 4G modem and ASUS router?

If the 4G modem needs an IP address you could assign one that is outside the DHCP range of the Asus router but in the same subnet.

From a cabling point of view, is this correct?

Antenna to 4G modem in bridge mode, cat5 to PoE switch, cat5 to router WAN. Then cat5 from router LAN back to PoE switch, cat5 to all wired devices.

Normally you'd plug the WAN port of your ASUS into the 4G modem, then configure the ASUS/modem for bridge mode.

Then you'd plug one of your ASUS LAN ports into your switch.

Which of course in your case isn't going to work, as you need PoE to the modem. And you probably can't just plug them all into a single switch (because the ASUS may well need to do bridging on its WAN port and the modem probably sends all its bridged traffic to the first device it sees talking on the LAN, not all bridging setups are the same).

You're probably going to need a second switch. The ASUS has a four port switch, do you have more than four other wired devices ?

Hmm... I thought it might be a problem. I wish I had bought a small 4-port PoE Switch now rather than a 16-port one.

I do still have my dumb non-PoE Switch but would really prefer not to have the two switches powered at the same time but it looks like it is the only way to do this tidily.

4G modem in Bridge mode to PoE Switch - PoE Switch to Router WAN - Router LAN to non-PoE Switch - wired devices to non-PoE Switch.

In reply to a post by DanielCoffey67:

Hmm... I thought it might be a problem. I wish I had bought a small 4-port PoE Switch now rather than a 16-port one.

If you have only the one device to power with PoE, you can get a PoE injector:
https://www.amazon.co.uk/TP-LINK-TL-PoE150S-Injector...

I have a cheap PoE injector but given that the entire house is networked I thought a single PoE switch would be more elegant and efficient.

Prior to getting the outdoor modem, we had no PoE devices so the old 16-port switch was tidy and sufficient. Now we have the first PoE device, rather than running the old switch plus a cheap PoE injector, I had thought a single new PoE switch would keep everything tidy.

Of course I now understand that we will end up having two wall transformers running regardless... either a PoE injector and the old switch or the PoE switch and the old switch.

If I keep both switches running then they will be in a cupboard out of sight on a UPS so I'll do it that way.

In reply to a post by DanielCoffey67:

I have a cheap PoE injector but given that the entire house is networked I thought a single PoE switch would be more elegant and efficient.

That works well if you have, e.g. VoIP phones or cameras, inside the house. But you are trying to use one switch to manage the "outside" and "inside" parts of your network at the same time. Its just a level of complexity that could easily introduce problems in the future when something isn't working properly.