02 November 2014

Cable Modem and DSL Home Networks Using VLANs Sharing Ethernet with DD-WRT in Control

This article continues the VLAN discussion from the previous post,  showing you the settings for DD-WRT to make an isolated LAN sharing Ethernet wiring between you and a roommate in the common areas of your home.  This requires installing custom firmware from DD-WRT or OpenWRT.  The included video shows a real world setup that matches the article, but simulates some components described herein.  The cable colorings match the diagram with VLAN7 in yellow and the trunk lines in orange.

I assume you have two networks in your home such as cable and DSL for you and your roommate and you want to use wired networking with access to both networks in common areas with only one Ethernet cable per room. VLANs are a great solution for this. Let's say your roommate needs  a connection in the office and one for the downstairs TV for her entertainment device (XBOX, AppleTV, etc), thus you two need to share the Ethernet cable for common rooms.  For this scenario, we will split the trunk into a Y configuration, bridging two physically separate cables together with VLAN tagging and trunking sending both LANs to two floors in the home.

Home Shares DSL and Cable in Wired Ethernet Using VLANs with DD-WRT, OpenWRT, and VLAN Trunks
Home Network Carrying  multiple VLANs

We will assign your roommate VLAN7 in the basement distribution switch (switch2), but we'll exclude the Netgear WNDR3800 basement router since which serves the cable modem.  In the prior article, you see the basement switch (switch2) as a VLAN distribution point, but it will become a VLAN access point for VLAN7.

Switch 2 changes from the previous build by adding a second trunk to the first floor switch (switch3). Port 3 is now tagged and includes both VLAN1 for the homeowner LAN, and VLAN7 the DSL LAN.  Port 2 is assigned to VLAN7's DSL modem which is simulated with a laptop in the video  Switch2 doesn't include VLAN7 in the Wan port (W) column excluding it from being able to receive VLAN7 traffic.

Image shows two VLAN trunks and one port assigned to VLAN7
DD-WRT VLAN Trunks and Ports on Linksys e3000

This is the first floor DD-WRT router using the venerable Linksys WRT54GS router.  In this configuration, port 4 is assigned to VLAN7, while the remaining ports stay on VLAN1 except for the WAN port which is the trunk line from the basement.  This router supports the roommate's living room device on port 4.  The video uses my receiver to simulate the roommate's device.

This diagram tags the VLAN trunk port and assigns the VLANs to their proper ports
Linksys WRT54GS VLAN Trunk

The 2nd floor VLAN distribution runs DD-WRT on a Linksys e3000 and uses port 4 for VLAN7 and supports the roommate's computer in the office.

This image shows VLAN7 on its own port, the WAN port as a trunkline, and the remaining ports on VLAN1

Electric wiring or wireless technologies can also be used to connect different networks to devices around the home and these solutions tend to be the the star attraction when you inquire at places like Micro Center or Best Buy for help, but you have another very powerful technique in VLANs which can be used with the inexpensive equipment you or others have discarded.  You can also find many managed switches under $100 U.S. if you wish to purchase hardware dedicated to VLAN networks.