FTTC modem-router connection over VLAN link

Afternoon all

I'm currently planning a rejig to my home network to give more capability, expandability and coverage...

Currently, I've got BT Infinity 2 with a HH5. However the signal doesn't all of my 1900's Victorian brick-built end-terrace house
So I'm planning to replace the HH5 with an Openreach modem and EdgeRouter-Lite, with 1 or 2 Unifi AP-LR wifi units.

Currently, my BT master socket is in my dining room, but I'd like to locate the ERL upstairs in my office with the rest of my computer equipment.
I've got a 1Gbe socket next to my master socket, which currently runs up into my office. The plan is to put a TP-Link TL-SG2008 at either end of said 1Gbe link, which will allow me to use VLANs. I might even run a 2nd 1Gbe connection and LAG them.

So my main question is is it possible to plug the LAN side port of the Openreach modem into the downstairs switch on an untagged port, and then connect the ERL to the same VLAN upstairs?
Any major down-sides/issues with doing that?

Cheers in advance for any replies.

Regards
Gavin

In reply to a post by fatmcgav:

So my main question is is it possible to plug the LAN side port of the Openreach modem into the downstairs switch on an untagged port, and then connect the ERL to the same VLAN upstairs?
Any major down-sides/issues with doing that?

There's no problem doing this. My Openreach modem is connected to an untagged port on my switch, which has a VLAN ID dedicated to the task. The traffic is tagged on the router port, which also carries other VLANs with their respective tags.

If you are reading this message, it works!

In reply to a post by David_W:

In reply to a post by fatmcgav:

So my main question is is it possible to plug the LAN side port of the Openreach modem into the downstairs switch on an untagged port, and then connect the ERL to the same VLAN upstairs?
Any major down-sides/issues with doing that?

There's no problem doing this. My Openreach modem is connected to an untagged port on my switch, which has a VLAN ID dedicated to the task. The traffic is tagged on the router port, which also carries other VLANs with their respective tags.

If you are reading this message, it works!

Cool, cheers for confirming...

I keep seeing VLAN 101 mentioned when googling this subject. Does it need to stick to that one, or am I free to choose?

Cheers
Gav

The modem is using VLAN 101 outbound, not towards the home LAN. You can use whatever you want on your LAN, the modem shouldn't see the tag.

VLAN 101 is used on the VDSL side, the modem 'LAN' side is untagged.

Cheers both...

In reply to a post by fatmcgav:

I keep seeing VLAN 101 mentioned when googling this subject. Does it need to stick to that one, or am I free to choose?

As others have said, the LAN side is untagged by default, so you can use whichever ID you like.

If you leave this traffic untagged, make sure you set the VLAN settings (including the PVID) appropriately on the switch port - you'd want to make the port a member of the appropriate VLAN, with no tagging. You set the PVID set to the VLAN ID so that the switch knows which VLAN untagged traffic on that port belongs to.


If you have a hacked HG612, you can configure LAN side tagging in the web interface, though I wouldn't recommend this as it means you can't replace a failed modem without first making the same configuration change to the modem.


VLANs are simple once you understand what is going on, but it's very easy to make a mistake in configuring them. If things are not working, double check the settings on the switch(es) - you may well have something that is not quite correct.

In my system, the modem is in one building, and the router is a rack mount server in another building on a different switch. The two switches have a couple of duplex fibre links between them, carrying several networks using VLAN tagging.