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I have a modem in my basement and need to connect the modem directly to an ethernet switch. The reason for this is because I only have 1 cat5 cable going to the location of the router on the main floor of my house.

So my plan is to plug the cable modem into a network switch in the basement and connect the Cat5 cable going to the main floor into the network switch as well. After speaking with Google OnHub support, they told me that in order for me to do this I would need to do this with a network switch that supports Vlan.

I have no clue how I would do this or what network switch I need to purchase. Any help explaining what I need to do and what I need to purchase would be very much appreciated.

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    Did the support personnel explain why they thought you would need a switch which supports VLANs? Most home use switches have no VLAN configuration options and I can't see why one would be needed for your requirements.
    – Mark Riddell
    Aug 20, 2016 at 15:48
  • If I can remember correctly it had something to do with managing the IP address from my ISP. He said that I can't connect the modem directly into a switch and then plug the router that is upstairs into that switch. To do this he said I need to have a Vlan network switch to manage the IP address going to the router upstairs.
    – GJP
    Aug 20, 2016 at 15:52
  • Sounds like BS to me. As long as both devices (router and modem) use Ethernet, it will work.
    – Daniel B
    Aug 20, 2016 at 17:19

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So, here's why you don't need a VLAN-aware switch.

First, what is VLAN? There are two things called VLAN. One is inside a switch. This is called port-based VLAN. There is also "VLAN on the wire", called VLAN tagging/trunking.

Usually, every port on a switch can communicate with all other ports. On virtually all managed switches, you can restrict this by putting the ports into groups that are isolated, effectively making one switch into two separate switches. This is called port-based VLAN. All this happens inside the switch and requires no cooperation from other devices.

Then there is VLAN tagging (also called VLAN trunking, 802.1Q). It is specific to Ethernet (802.3) networks. It specifies an additional header inside an Ethernet frame that contains a number, the so-called VLAN ID. This way, up to 4094 virtual "cables" can run over a single Ethernet connection, hence trunking. Because the on-wire data structure is different from regular Ethernet frames, device/software cooperation is required. However, to a regular switch, it's an Ethernet frame like any other. It has its destination and source MAC addresses in the usual places.

Here's an image from Wikipedia:

802.1Q frame

The two techniques can be combined: A port on a switch can be set to belong to multiple groups. To maintain isolation, the data is transmitted tagged.

In your use case, the switches would simply function as "range extenders", whether necessary or not. They don't interact with the data transmitted and the don't need to.

So even if the data between modem and router were split into VLANs, it wouldn't matter.

There are indeed ISPs that use VLAN tagging, for example Deutsche Telekom with its "Entertain" IPTV service. Regular Internet access works via PPPoE on VLAN 7. IPTV is available via DHCP on VLAN 8. It relies on a provider-operated multicast network.

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As long as the modem and the router on main floor are not further apart than 100 m (100 yards) you could use the only cable to directly connect modem and router. Your PC(s) would then be plugged in at the router.

This will avoid having to
- buy a VLAN capable switch
- find out which VLAN IDs are used by your ISP
- configure the switch ports to let the VLANs used pass

which for a layman is not that easy.

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